Thermoassociative and exchangeable copolymers, composition comprising same

ABSTRACT

Compositions resulting from the mixing of at least one copolymer A1, resulting from the copolymerization of at least one monomer functionalized by diol functions with at least one styrenic monomer, and at least one compound A2 comprising at least two boronic ester functions. They have very varied rheological properties depending on the proportion of compounds A1 and A2 used. Composition resulting from the mixing of at least one lubricating oil with such a composition of associative and exchangeable polymers and use of this composition for lubricating a mechanical part.

The invention relates to a composition resulting from the mixing of atleast one copolymer A1, resulting from the copolymerization of at leastone monomer functionalized with diol functions with at least one styrenemonomer, and of at least one compound A2 comprising at least two boronicester functions. Such compositions have very varied rheologicalproperties depending on the proportion of the compounds A1 and A2 used.The invention also relates to a composition resulting from the mixing ofat least one lubricant oil with such a polymer composition and to theuse of this composition for lubricating a mechanical part.

The field of the invention is that of exchangeable associative polymersand that of lubricants.

PRIOR ART

High molar mass polymers are widely used for increasing the viscosity ofsolutions in many fields, such as the petroleum, paper and watertreatment industries, the mining industry, the cosmetics and textileindustries and in general in all the industrial techniques usingthickened solutions.

However, these high molecular mass polymers have the drawback ofundergoing substantial irreversible degradation under mechanical stresswhen compared with the same polymers of smaller sizes. These shearstresses on high molar mass polymers lead to cleavages in themacromolecular chains. The polymer thus degraded undergoes a reductionin or disappearance of its thickening properties, and the viscosity ofsolutions containing it drops irreversibly. This loss of shear strengthleads to degradation of the properties of solutions based on high molarmass polymers.

Patent applications WO2015/110642, WO2015/110643 and WO2016113229disclose a composition resulting from the mixing of at least onecopolymer A1 resulting from the copolymerization of at least one monomerfunctionalized with diol functions and of at least one compound A2comprising at least two boronic ester functions. These compounds canassociate, to optionally form a gel, and to exchange chemical bondsthermoreversibly. These additives have the advantage of reducing thedrop in viscosity of the solution comprising them when the temperatureincreases. These polymer compositions have very varied rheologicalproperties depending on the proportion of the compounds A1 and A2 used.They may also comprise a diol compound which makes it possible to bettercontrol the association of the two copolymers.

In particular, these polymer compositions may be added to a lubricantoil to lubricate a mechanical part. These copolymers make it possible toformulate lubricant compositions whose viscosity is better controlledwhen compared with the lubricant compositions of the prior art. Inparticular, when they are introduced into a base oil, these copolymershave a tendency to reduce the drop in viscosity of the mixture when thetemperature increases. The presence of a diol compound in theselubricant compositions makes it possible to better modify theirviscosity.

Lubricant compositions are compositions applied between surfaces,especially metal surfaces, of moving parts. They make it possible toreduce the friction and the wear between two parts in contact and inmotion relative to each other. They also serve to dissipate part of thethermal energy generated by this friction. Lubricant compositions form aprotective film between the surfaces of the parts onto which they areapplied.

The compositions used for lubricating mechanical parts are generallyformed from a base oil and additives. The base oil, which is especiallyof petroleum or synthetic origin, shows viscosity variations when thetemperature is varied.

Specifically, when the temperature of a base oil increases, itsviscosity decreases, and when the temperature of the base oil decreases,its viscosity increases. Now, in a hydrodynamic lubrication regime, thethickness of the protective film is proportional to its viscosity, andthus also depends on the temperature. A composition has good lubricantproperties if the thickness of the protective film remains substantiallyconstant irrespective of the conditions and the duration of use of thelubricant.

In an internal combustion engine, a lubricant composition may besubjected to external or internal temperature changes. The externaltemperature changes are due to variations in the temperature of theambient air, for instance variations in temperature between summer andwinter. The internal temperature changes result from the running of theengine. The temperature of an engine is lower during its start-up phase,especially in cold weather, than during prolonged use. Consequently, thethickness of the protective film may vary in these different situations.

There is therefore a need to provide a lubricant composition which hasgood lubricant properties and whose viscosity is sparingly subject totemperature variations.

It is known practice to add additives that improve the viscosity of alubricant composition. The function of these additives is to modify therheological behavior of the lubricant composition. They make it possibleto promote greater stability of the viscosity over a temperature rangewithin which the lubricant composition is used. For example, theseadditives limit the reduction in viscosity of the lubricant compositionwhen the temperature rises, while at the same time limiting the increasein viscosity under cold conditions.

Additives for enhancing the viscosity (or additives for enhancing theviscosity index) ensure good lubrication by limiting the impact on theviscosity under cold conditions and by ensuring a minimum thickness ofthe film under hot conditions. The viscosity-enhancing additivescurrently used are polymers such as olefin copolymers (OCP) andpolyalkyl methacrylates (PMA). These polymers have high molar masses. Ingeneral, the contribution of these polymers toward controlling theviscosity is proportionately greater the higher their molecular weight.

However, high molar mass polymers have the drawback of having poorpermanent shear strength when compared with polymers of the same natureand of the same architecture but of smaller size.

Now, a lubricant composition is subjected to high shear stressesespecially in internal combustion engines, where the friction surfaceshave a very small separation and the pressure is exerted on the partsare high. These shear stresses on high molar mass polymers lead tocleavages in the macromolecular chains. The polymer thus degradedundergoes a reduction in its thickening properties, and the viscositydrops irreversibly. Permanent shear strength thus leads to degradationof the lubricant properties of the lubricant composition.

Finally, compositions have been sought which have better oxidationstability, in particular better resistance to oxidation by freeradicals.

The compositions described in patent applications WO 2015/110642, WO2015/110643 and WO 2016/113229 have very advantageous properties, as aresult of their capacity to form thermoreversible associations. However,it has been found that, under certain conditions, especially hightemperature conditions, the associative behavior of these copolymersreduced. In particular, a reduction in the viscosity index of lubricantcompositions comprising them, and poorer resistance to cycling (whichmay be defined as the succession of sequences of raising and lowering ofthe temperature as is observed in an engine), leading to a loss of thelubricant properties over time, have been observed.

Thus, the Applicant set itself the objective of preparing novelcopolymers which have improved properties when compared with thecopolymers of the prior art.

This objective is achieved by means of novel rheological additives whichcan associate, optionally to form a gel, and can be thermoreversiblyexchanged. In contrast with the base oil which becomes fluidized whenthe temperature increases, the additives of the present invention havethe advantage of thickening the medium in which they are dispersed whenthe temperature increases, and they maintain this advantage at hightemperatures, for instance up to 150° C. These additives show resistanceto temperature increase when compared with the additives of the priorart.

Lubricant compositions comprising them show better stability of theircycling performance and better reproducibility of the lubricantproperties over time.

This characteristic results from the combined use of two particularcompounds, a copolymer bearing diol functions and styrene functions anda compound comprising boronic ester functions.

It is possible, by means of the compositions of the invention, toprovide lubricant compositions which have good lubricant propertiesduring the start-up phases of an engine (cold phase) and good lubricantproperties when the engine is running at its service temperature (hotphase).

SUMMARY OF THE INVENTION

A first subject of the invention consists of a composition resultingfrom the mixing of at least

-   -   one polydiol random copolymer A1 comprising at least from 2 mol        % to 50 mol % of at least one monomer M3 of general formula (X):

in which:

-   -   Z₁, Z₂ and Z₃, which may be identical or different, represent        groups chosen from a hydrogen atom, a C1-C12 alkyl, and a group        —OZ′ or —C(O)—O—Z′ with Z′ being a C1-C12 alkyl, and    -   a compound A2 comprising at least two boronic ester functions.

According to a preferred embodiment of the invention, the randomcopolymer A1 results, directly or indirectly, from the copolymerization:

-   -   of at least one first monomer M1 of general formula (I):

in which:

-   -   R₁ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   x is an integer ranging from 1 to 18 and preferably from 2 to        18;    -   y is an integer equal to 0 or 1;    -   X₁ and X₂, which may be identical or different, are chosen from        the group formed by hydrogen, tetrahydropyranyl,        methyloxymethyl, tert-butyl, benzyl, trimethylsilyl and        t-butyldimethylsilyl;        or    -   X₁ and X₂ form, with the oxygen atoms, a bridge having the        following formula

in which:

-   -   the asterisks (*) symbolize the bonds to oxygen atoms,    -   R′₂ and R″₂, which may be identical or different, are chosen        from the group formed by hydrogen and a C₁-C₁₁ alkyl, preferably        methyl;        or    -   X₁ and X₂ form, with the oxygen atoms, a boronic ester having        the following formula:

in which:

-   -   the asterisks (*) symbolize the bonds to oxygen atoms,    -   R″₂ is chosen from the group formed by a C₆-C₃₀ aryl, a C₇-C₃₀        aralkyl and a C₂-C₃₀ alkyl, preferably a C₆-C₁₈ aryl;    -   with at least one second monomer M2 of general formula (II):

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   R₃ is chosen from the group formed by: —C(O)—O—R′₃;    -   —O—R′₃; —S—R′₃ and —C(O)—N(H)—R′₃ with R′₃ being a C₁-C₃₀ alkyl        group,        and    -   with at least one third monomer M3 of general formula (X):

in which:

-   -   Z₁, Z₂ and Z_(a), which may be identical or different, represent        groups chosen from a hydrogen atom, a C1-C12 alkyl, and a group        —OZ′ or —C(O)—O—Z′ with Z′ being a C1-C12 alkyl,

According to a preferred embodiment, the third monomer M3 is styrene.

According to a preferred embodiment, the random copolymer A1 results,directly or indirectly, from the copolymerization of at least onemonomer M1 with at least two monomers M2 bearing different groups R₃ andat least one monomer M3.

According to a first preferred variant, the two monomers M2 of therandom copolymer A1 have the general formula (II-B):

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   —R″₃ is a C₉-C₃₀ alkyl group.

According to another preferred variant, one of the monomers M2 of therandom copolymer A1 has the general formula (II-A):

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   R″₃ is a C₁-C₈ alkyl group;        and the other monomer M2 of the random copolymer A1 has the        general formula (II-B):

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂CH₃;    -   R′″₃ is a C₉-C₃₀ alkyl group.

According to a preferred embodiment, the side chains of the randomcopolymer A1 have a mean length ranging from 8 to 20 carbon atoms,preferably from 9 to 18 carbon atoms.

According to a preferred embodiment, the random copolymer A1 has a molarpercentage of monomer M3 of formula (X) in said copolymer ranging from3% to 40% and more preferably ranging from 5% to 35%.

According to a preferred embodiment, the random copolymer A1 has a molarpercentage of monomer M1 of formula (I) in said copolymer ranging from1% to 30% and preferably from 5% to 25%.

According to a preferred embodiment, the random copolymer A1 has anumber-average degree of polymerization ranging from 40 to 2000 andpreferably from 40 to 1000.

According to a preferred embodiment, the random copolymer A1 has apolydispersity index (Ip) ranging from 1.05 to 4.0, preferably rangingfrom 1.10 to 3.8.

According to a first preferred embodiment, compound A2 is a compound offormula (III):

in which:

-   -   w₁ and w₂, which may be identical or different, are integers        chosen between 0 and 1;    -   R₄, R₅, R₆ and R₇, which may be identical or different,        represent a group chosen from a hydrogen atom, a        hydrocarbon-based group comprising from 1 to 30 carbon atoms,        preferably between 4 and 18 carbon atoms and even more        preferentially between 6 and 14 carbon atoms, said        hydrocarbon-based group being optionally substituted with one or        more groups chosen from: a hydroxyl, a group —OJ or —C(O)—O-J        with J being a hydrocarbon-based group comprising from 1 to 24        carbon atoms;    -   L is a divalent bonding group chosen from the group formed by a        C₆-C₁₈ aryl, a C₇-C₂₄ aralkyl and a C₂-C₂₄ hydrocarbon-based        chain.

According to another preferred embodiment, compound A2 is a randomcopolymer resulting from the copolymerization

-   -   of at least one monomer M4 of formula (IV):

in which:

-   -   t is an integer equal to 0 or 1;    -   u is an integer equal to 0 or 1;    -   M and R₈ are identical or different divalent bonding groups,        chosen from the group formed by a C₆-C₁₈ aryl, a C₇-C₂₄ aralkyl        and a C₂-C₂₄ alkyl, preferably a C₆-C₁₈ aryl,    -   X is a function chosen from the group formed by —O—C(O)—,        —C(O)—O—, —C(O)—N(H)—, —N(H)—C(O)—, —S—, —N(H)—, —N(R′₄)— and        —O— with R′₄ being a hydrocarbon-based chain comprising from 1        to 15 carbon atoms;    -   R₉ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   R₁₀ and R₁₁, which may be identical or different, represent a        group chosen from a hydrogen atom, a hydrocarbon-based group        comprising from 1 to 30 carbon atoms, preferably between 4 and        18 carbon atoms and even more preferentially between 6 and 14        carbon atoms, said hydrocarbon-based group being optionally        substituted with one or more groups chosen from: a hydroxyl, a        group —OJ or —C(O)—O-J with J being a hydrocarbon-based group        comprising from 1 to 24 carbon atoms;    -   with at least one second monomer M5 of general formula (V):

in which:

-   -   R₁₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;        R₁₃ is chosen from the group formed by a C₆-C₁₈ aryl, a C₆-C₁₈        aryl substituted with a group R′₁₃, —C(O)—O—R′₁₃; —O—R′₁₃,        —S—R′₁₃ and —C(O)—N(H)—R′₁₃ with R′₁₃ being a C₁-C₃₀ alkyl        group.

According to a preferred embodiment, at least one of the following threeconditions is met:

-   -   either, in formula (IV): u=1, R₉ is H and R₈ represents a C₆-C₁₈        aryl or a C₇-C₂₄ aralkyl and the double bond of the monomer M4        of formula (IV) is directly connected to the aryl group;    -   or, in formula (V): R₁₂ represents H and R₁₃ is chosen from the        group formed by a C₆-C₁₈ aryl and a C₆-C₁₈ aryl substituted with        a group R′₁₃ with R′₁₃ being a C₁-C₂₅ alkyl group and the double        bond of the monomer M5 of formula (V) is directly connected to        the aryl group.    -   or, copolymer A2 comprises at least one third monomer M3 of        formula (X)

in which:

-   -   Z₁, Z₂ and Z₃, which may be identical or different, represent        groups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and a group        —OZ′ or —C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl.

Advantageously, when A2 comprises a third monomer M3 of formula (X),this monomer M3 is styrene.

Advantageously, the boronic ester random copolymer A2 has a molarpercentage of styrene monomer(s), advantageously of styrene, of formula(IV), (V) and/or (X), in said copolymer ranging from 2 mol % to 50 mol%, preferentially from 3 mol % to 40 mol % and more preferably from 5mol % to 35 mol %.

According to an advantageous embodiment, a chain formed by the sequenceof groups R₁₀, M, X and (R₈)_(u) with u equal to 0 or 1 of the monomerof formula (IV) has a total number of carbon atoms ranging from 8 to 38and preferably from 10 to 26.

According to an advantageous embodiment, the side chains of thecopolymer A2 have a mean length of greater than or equal to 8 carbonatoms, preferably from 11 to 16 carbon atoms.

According to an advantageous embodiment, the copolymer A2 has a molarpercentage of monomer of formula (IV) in said copolymer ranging from0.25% to 30% and preferably from 1% to 25%.

According to an advantageous embodiment, the copolymer A2 has anumber-average degree of polymerization ranging from 50 to 1500 andpreferably from 50 to 800.

According to a preferred embodiment, the random copolymer A2 has apolydispersity index (Ip) ranging from 1.04 to 3.54, preferably rangingfrom 1.10 to 3.10.

According to a preferred embodiment, the content of copolymer A1 rangesfrom 0.1% to 50% by weight relative to the total weight of thecomposition.

According to a preferred embodiment, the content of compound A2 rangesfrom 0.1% to 50% by weight relative to total weight of the composition.

According to a preferred embodiment, the mass ratio between copolymer A1and compound A2 (ratio A1/A2) ranges from 0.005 to 200, preferably from0.05 to 20 and even more preferably from 0.1 to 10.

According to a preferred embodiment, the copolymer A1 has been obtainedvia a process comprising at least:

-   -   one step of radical polymerization controlled by reversible        addition-fragmentation chain transfer in the presence of a        transfer agent of thiocarbonylthio type.

A more preferred embodiment, the copolymer A1 has been obtained via aprocess comprising at least, after the polymerization:

-   -   one step of aminolysis of the thiocarbonylthio residue to thiol,        followed by    -   Michael addition on an acrylate to transform the thiol into a        thioether.

According to a preferred embodiment, the composition also comprises atleast one exogenous compound A4 chosen from 1,2-diols and 1,3-diols.

According to a preferred embodiment, the molar percentage of exogenouscompound A4 relative to the boronic ester functions of the randomcopolymer A2 ranges from 0.025% to 5000%, preferably from 0.1% to 1000%,even more preferably from 0.5% to 500% and even more preferably from 1%to 150%.

According to a preferred embodiment, the exogenous compound A4 has thegeneral formula (VI):

with:w₃ being an integer equal to 0 or 1;R₁₄ and R₁₅, which may be identical or different, chosen from the groupformed by hydrogen and a hydrocarbon-based group containing from 1 to 24carbon atoms.

A subject of the invention is also a process for preparing a compositionas described above, which comprises the mixing of at least one polydiolrandom copolymer A1 and of at least one compound A2 comprising at leasttwo boronic ester functions, in which the copolymer A1 has been obtainedvia a process comprising at least:

-   -   one step of radical polymerization controlled by reversible        addition-fragmentation chain transfer in the presence of a        transfer agent of thiocarbonylthio type.

According to a preferred embodiment of the process, the copolymer A1 hasbeen obtained via a process comprising at least, after thepolymerization:

-   -   one step of aminolysis of the thiocarbonylthio residue to thiol,        followed by    -   Michael addition on an acrylate to transform the thiol into a        thioether.

The invention also relates to a lubricant composition resulting from themixing of at least:

-   -   one lubricant oil; and    -   one composition as defined above and as detailed in the        description below.

According to a preferred embodiment, the lubricant oil is chosen fromoils of group I, of group II, of group III, of group IV and of group Vof the API classification, and a mixture thereof.

According to a preferred embodiment, the lubricant composition resultsfrom the mixing also with a functional additive chosen from the groupformed by antioxidants, detergents, anti-wear additives,extreme-pressure additives, viscosity-index-enhancing polymers,flow-point improvers, antifoams, anticorrosion additives, thickeners,dispersants, friction modifiers, and mixtures thereof.

The invention also relates to a process for modifying the viscosity of alubricant composition, the process comprising at least:

-   -   the provision of a composition as defined above and as detailed        in the description below,    -   the mixing of this composition with a lubricant oil.

DETAILED DESCRIPTION

Additive Composition According to the Invention:

One subject of the present invention is a composition ofthermoreversibly associative and exchangeable compounds, thiscomposition resulting from the mixing of at least

-   -   one polydiol random copolymer A1 as described below or as may        especially be obtained via one of the processes described below,        this polymer comprising optionally substituted benzyl groups;    -   one compound A2 comprising at least two boronic ester functions.

This additive composition makes it possible to control and modify therheological behavior of a medium into which it is added. The medium maybe a hydrophobic medium, especially an apolar medium, such as a solvent,a mineral oil, a natural oil or a synthetic oil.

Polydiol Random Copolymers A1

The polydiol random copolymer A1 comprises at least one monomer M3, ofgeneral formula (X) defined above. The other monomers included in thecomposition of the polydiol random copolymer A1 must be compatible withcopolymerization with monomers M3.

According to a preferred embodiment, the polydiol random copolymer A1results, directly or indirectly, from the copolymerization of at leastone first monomer M1 bearing diol functions, of at least one secondmonomer M2, different in chemical structure from that of the monomer M1,and of at least one third monomer M3, chosen from styrene and styrenederivatives. The term “results directly or indirectly” means that theprocess for preparing the copolymer may comprise one or more steps otherthan copolymerization, such as a deprotection step. The copolymerizationmay especially be optionally followed by a step of deprotecting the diolfunctions.

Throughout the description, the following expressions are used withoutpreference and equivalently: “the polydiol random copolymer A1 results,directly or indirectly, from the copolymerization” and “the polydiolrandom copolymer A1 results from the copolymerization”.

The term “copolymer” means a linear or branched oligomer ormacromolecule having a sequence formed from several repeating units (ormonomer units), of which at least two units have a different chemicalstructure.

The term “monomer unit” or “monomer” means a molecule that is capable ofbeing converted into an oligomer or a macromolecule by combination withitself or with other molecules of the same type. A monomer denotes thesmallest constituent unit whose repetition leads to an oligomer or amacromolecule.

The term “random copolymer” means an oligomer or a macromolecule inwhich the sequential distribution of the monomer units obeys knownstatistical laws. For example, a copolymer is said to be random when itis formed by monomer units whose distribution is a Markoviandistribution. A schematic random polymer (P1) is illustrated in FIG. 1.The distribution of the monomer units in the polymer chain depends onthe reactivity of the polymerizable functions of the monomers and on therelative concentration of the monomers. The polydiol random copolymersof the invention are different from block copolymers and gradientcopolymers. The term “block” denotes a part of a copolymer comprisingseveral identical or different monomer units and which has at least oneconstitutional or configurational feature allowing it to bedistinguished from its adjacent parts. A schematic random polymer (P3)is illustrated in FIG. 1. A gradient copolymer denotes a copolymer of atleast two monomer units of different structures, the monomer compositionof which changes gradually along the polymer chain, thus graduallypassing from one end of the polymer chain which is rich in one monomerunit, to the other end which is rich in the other comonomer. A schematicgradient polymer (P2) is illustrated in FIG. 1.

The term “copolymerization” means a process which makes it possible toconvert a mixture of at least two monomer units of different chemicalstructures into an oligomer or a copolymer.

In the rest of the present patent application, “B” represents a boronatom.

The term “C_(i)-C_(j) alkyl” means a linear or branched, saturatedhydrocarbon-based chain, comprising from i to j carbon atoms. Forexample, the term “C₁-C₁₀ alkyl” means a linear or branched, saturatedhydrocarbon-based chain comprising from 1 to 10 carbon atoms.

The term “C_(x)-C_(y) aryl” means a functional group which is derivedfrom an aromatic hydrocarbon-based compound comprising from x to ycarbon atoms. This functional group may be monocyclic or polycyclic. Byway of illustration, a C₆-C₁₈ aryl may be phenyl, naphthalene,anthracene, phenanthrene and tetracene.

The term “C_(x)-C_(y) alkenyl” means a linear or branchedhydrocarbon-based chain including at least one unsaturation, preferablya carbon-carbon double bond, and comprising from x to y carbon atoms.

The term “C_(x)-C_(y) aralkyl” means an aromatic, preferably monocyclic,hydrocarbon-based compound substituted with at least one linear orbranched alkyl chain and in which the total number of carbon atoms inthe aromatic ring and in its substituents ranges from x to y carbonatoms. By way of illustration, a C₇-C₁₈ aralkyl may be chosen from thegroup formed by benzoyl, tolyl and xylyl.

The term “C_(x)-C_(y) aryl substituted with a group Y” means anaromatic, preferably monocyclic, hydrocarbon-based compound comprisingfrom x to y carbon atoms, at least one carbon atom of the aromatic ringof which is substituted with a group Y.

The term “Hal” or “halogen” means a halogen atom chosen from the groupformed by chlorine, bromine, fluorine and iodine.

Monomer M1

The first monomer M1 of the polydiol random copolymer (A1) of theinvention has the general formula (I):

in which:

-   -   R, is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   x is an integer ranging from 1 to 18, preferably ranging from 2        to 18, more preferably from 3 to 8 and even more preferably x is        equal to 4;    -   y is an integer equal to 0 or 1; preferably, y is equal to 0;    -   X₁ and X₂, which may be identical or different, are chosen from        the group formed by hydrogen, tetrahydropyranyl,        methyloxymethyl, tert-butyl, benzyl, trimethylsilyl and        t-butyldimethylsilyl;        or    -   X₁ and X₂ form, with the oxygen atoms, a bridge having the        following formula

in which:

-   -   the asterisks (*) symbolize the bonds to oxygen atoms,    -   R′₂ and R″₂, which may be identical or different, are chosen        from the group formed by hydrogen and a C₁-C₁₁ alkyl group;        or    -   X₁ and X₂ form, with the oxygen atoms, a boronic ester having        the following formula:

in which:

-   -   the asterisks (*) symbolize the bonds to oxygen atoms,    -   R′″₂ is chosen from the group formed by a C₆-C₃₀ aryl, a C₇-C₃₀        aralkyl and a C₂-C₃₀ alkyl, preferably a C₆-C₁₈ aryl, more        preferably phenyl.

Preferably, when R′₂ and R″₂ are a C₁-C₁₁ alkyl group, thehydrocarbon-based chain is a linear chain. Preferably, the C₁-C₁₁ alkylgroup is chosen from the group formed by methyl, ethyl, n-propyl,n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl andn-undecyl. More preferably, the C₁-C₁₁ alkyl group is methyl.

Preferably, when R′″₂ is a C₂-C₃₀ alkyl group, the hydrocarbon-basedchain is a linear chain.

Among the monomers of formula (I), the monomers corresponding to formula(I-A) are among the preferred:

in which:

-   -   R₁ is chosen from the group formed by —H, —CH₃ and —CH₂—H₃,        preferably —H and —CH₃;    -   x is an integer ranging from 1 to 18, preferably ranging from 2        to 18, more preferably from 3 to 8 and even more preferably x is        equal to 4;    -   y is an integer equal to 0 or 1; preferably, y is equal to 0.

Among the monomers of formula (I), the monomers corresponding to formula(I-B) are among the preferred:

in which:

-   -   R₁ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   x is an integer ranging from 1 to 18, preferably ranging from 2        to 18, more preferably from 3 to 8 and even more preferably x is        equal to 4;    -   y is an integer equal to 0 or 1; preferably, y is equal to 0;    -   Y₁ and Y₂, which may be identical or different, are chosen from        the group formed by tetrahydropyranyl, methyloxymethyl,        tert-butyl, benzyl, trimethylsilyl and t-butyldimethylsilyl; or    -   Y₁ and Y₂ form, with the oxygen atoms, a bridge having the        following formula:

in which:

-   -   the asterisks (′) symbolize the bonds to oxygen atoms,    -   R′₂ and R″₂, which may be identical or different, are chosen        from the group formed by hydrogen and a C₁-C₁ alkyl group;        or    -   Y₁ and Y₂ form, with the oxygen atoms, a boronic ester having        the following formula:

in which:

-   -   the asterisks (*) symbolize the bonds to oxygen atoms,    -   R′″₂ is chosen from the group formed by a C₆-C₃₀ aryl, a C₇-C₃₀        aralkyl and a C₂-C₃₀ alkyl, preferably a C₆-C₁₈ aryl, more        preferably phenyl.

Preferably, when R′₂ and R″₂ are a C₁-C₁₁ alkyl group, thehydrocarbon-based chain is a linear chain. Preferably, the C₁-C₁₁ alkylgroup is chosen from the group formed by methyl, ethyl, n-propyl,n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl andn-undecyl. More preferably, the C₁-C₁₁ alkyl group is methyl.

Preferably, when R′″₂ is a C₂-C₃₀ alkyl group, the hydrocarbon-basedchain is a linear chain.

The synthesis of the polydiol random copolymer (A1) may comprise thecopolymerization of monomers (I-B) in protected form with othercomonomers, followed by deprotection of the diol functions of themonomers (I-B).

Production of the Monomer M1

The monomer M1 of general formula (I-A) is obtained by deprotection ofthe alcohol functions of the monomer of general formula (I-B) accordingto reaction scheme 1 below:

with R₁, Y₁, Y₂, x and y as defined in the general formula (I-B)described above.

The reaction for the deprotection of the diol functions of the monomerof general formula (I-B) is well known to a person skilled in the art.Said person knows how to adapt the deprotection reaction conditions as afunction of the nature of the protecting groups Y₁ and Y₂.

The monomer M1 of general formula (I-B) may be obtained by reaction of acompound of general formula (I-c) with an alcohol compound of generalformula (I-b) according to reaction scheme 2 below:

in which:

-   -   Y₃ is chosen from the group formed by a halogen atom, preferably        chlorine, —OH and O—C(O)—R′₁ with R′₁ chosen from the group        formed by —H, —CH₃ and —CH₂—CH₃, preferably —H and —CH₃;    -   R₁, Y₁, Y₂, x and y have the same meaning as that given in the        general formula (I-B).

These coupling reactions are known to those skilled in the art.

The compound of general formula (I-c) is commercially available from thesuppliers: Sigma-Aldrich® and Alfa Aesar®.

The alcohol compound of general formula (I-b) is obtained from thecorresponding polyol of formula (I-a) by protection of the diolfunctions according to reaction scheme 3 below:

with x, y, Y₁ and Y₂ as defined in the general formula (I-B).

The reaction for the protection of the diol functions of the compound ofgeneral formula (I-a) is well known to a person skilled in the art. Saidperson knows how to adapt the protection reaction conditions as afunction of the nature of the protecting groups Y₁ and Y₂ used.

The polyol of general formula (I-a) is commercially available from thesuppliers: Sigma-Aldrich® and Alfa Aesar®.

Examples of synthesis of the monomers M1 are illustrated in theexperimental section of patent applications WO2015/110642, WO2015/110643and WO2016113229.

Monomer M2

The second monomer of the copolymer of the invention has the generalformula (II):

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   R₃ is chosen from the group formed by a C₆-C₁₈ aryl group, a        C₆-C₁₈ aryl substituted with a group R′₃, —C(O)—O—R′₃; —O—R′₃,        —S—R′₃ and —C(O)—N(H)—R′₃, with R′₃ being a C₁-C₃₀ alkyl group.

Preferably, R′₃ is a C₁-C₃₀ alkyl group, the hydrocarbon-based chain ofwhich is linear.

Among the monomers of formula (II), the monomers corresponding toformula (II-A) are among the preferred:

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   R″₃ is a C₁-C₈ alkyl group;

The term “C₁-C₈ alkyl group” means a linear or branched, saturatedhydrocarbon-based chain containing from 1 to 8 carbon atoms. Preferably,the hydrocarbon-based chain is linear.

Among the monomers of formula (II), the monomers corresponding toformula (II-B) are also among the preferred:

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   R′″₃ is a C₉-C₃₀ alkyl group.

The term “C₉-C₃₀ alkyl group” means a linear or branched, saturatedhydrocarbon-based chain containing from 9 to 30 carbon atoms.Preferably, the hydrocarbon-based chain is linear.

Production of the Monomer M2

The monomers of formulae (II), (II-A) and (II-B) are well known to thoseskilled in the art. They are sold by Sigma-Aldrich® and TCI®.

Monomer M3

The third monomer of the random copolymer of the invention has thegeneral formula (X):

in which:

-   -   Z₁, Z₂ and Z₃, which may be identical or different, represent        groups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and a group        —OZ′ or —C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl.

The term “C₁-C₁₂ alkyl group” means a linear or branched, saturatedhydrocarbon-based chain containing from 1 to 12 carbon atoms.Preferably, the hydrocarbon-based chain is linear. Preferably, thehydrocarbon-based chain comprises from 1 to 6 carbon atoms.

Advantageously, Z₁, Z₂ and Z₃, which may be identical or different,represent groups chosen from a hydrogen atom, a C₁-C₄ alkyl, and a group—OZ′ or —C(O)—O—Z′ with Z′ being a C₁-C₆ alkyl.

More preferably, Z₁, Z₂ and Z₂, which may be identical or different,represent groups chosen from a hydrogen atom, a C₁-C₄ alkyl, and a group—OZ or —C(O)—O—Z′ with Z′ being a C₁-C₄ alkyl.

Among the preferred monomers M3, mention may be made of: styrene,para-tert-butylstyrene, para-methoxystyrene, para-acetoxystyrene and2,4,6-trimethylstyrene.

According to a preferred embodiment, M3 is styrene.

Production of the Monomer M3

Certain monomers of formula (X), such as styrene,para-tert-butylstyrene, para-methoxystyrene, para-acetoxystyrene and2,4,6-trimethylstyrene, are well known to those skilled in the art. Theyare sold especially by Sigma-Aldrich®. Other monomers may be preparedfrom these commercial monomers via synthetic methods that are well knownto those skilled in the art.

Preferred Polydiol Copolymers

In one embodiment, a preferred random copolymer results from thecopolymerization of at least:

-   -   one first monomer M1 of general formula (I) as described        previously; especially of general formula (I-A) as described        previously;    -   one second monomer M2 of formula (II) as described previously,        in which R₂ is —CH₃ and R₃ is a group —C(O)—O—R′₃ with —R′₃        being a C₁-C₃₀ alkyl;    -   one third monomer M3 of general formula (X) as described        previously; especially styrene.

In another embodiment, a preferred random copolymer results from thecopolymerization of at least:

-   -   one first monomer M1 of general formula (I) as described        previously; especially of general formula (I-A) as described        previously,    -   one second monomer M2 of formula (II-B) as described previously;    -   one third monomer M2 of formula (II-B) as described previously,        which is different from the first monomer of formula (II-B); and    -   one fourth monomer M3 of general formula (X) as described        previously, especially styrene.

According to this other embodiment, a preferred random copolymer resultsfrom the copolymerization of at least:

-   -   one first monomer M1 of general formula (i) as described        previously; especially of general formula (I-A) as described        previously;    -   one second monomer M2 of formula (II-8) in which R₂ is —CH₃ and        R′″₃ is a C₉-C₃₀ alkyl group, preferably a linear C₉-C₃₀ alkyl        and better still a linear C₉-C₁₅ alkyl;    -   one third monomer M2 of formula (II-B), different from the        second monomer of formula (II-B), in which R₂ is —CH₃ and R′″₃        is a C₉-C₃₀ alkyl group, preferably a linear C₉-C₃₀ alkyl,        better still a linear C₁₆-C₂₄ alkyl; and    -   one fourth monomer M3 of general formula (X) as described        previously, especially styrene.

According to this embodiment, a preferred random copolymer results fromthe copolymerization of at least:

-   -   one first monomer M1 of general formula (i) as described        previously; especially of general formula (I-A) as described        previously,    -   one second monomer M2 chosen from the group formed by n-decyl        methacrylate and n-dodecyl methacrylate;    -   one third monomer M2 chosen from the group formed by palmityl        methacrylate, stearyl methacrylate, arachidyl methacrylate and        behenyl methacrylate,    -   optionally, one fourth monomer M3 of general formula (X) as        described previously, especially styrene.

In another embodiment, a preferred random copolymer results from thecopolymerization of at least:

-   -   one first monomer M1 of general formula (I) as described        previously; especially of general formula (I-A) as described        previously;    -   one second monomer M2 of formula (II-A) as described previously;        and    -   one third monomer M2 of formula (II-B) as described previously,    -   one fourth monomer M3 of general formula (X) as described        previously, especially styrene.

According to this other embodiment, a preferred random copolymer resultsfrom the copolymerization of at least:

-   -   one first monomer M1 of general formula (I) as described        previously; especially of general formula (I-A) as described        previously;    -   one second monomer M2 of formula (II-A) in which R₂ is —CH₃ and        R″₃ is a C₁-C₈ alkyl group, preferably a linear C₁-C₈ alkyl;    -   one third monomer M2 of formula (II-B) in which R₂ is —CH₃ and        R′″₃ is a C₉-C₃₀ alkyl group, preferably a linear C₉-C₃₀ alkyl;    -   one fourth monomer M3 of general formula (X) as described        previously, especially styrene.

According to this embodiment, a preferred random copolymer results fromthe copolymerization of at least:

-   -   one first monomer M1 of general formula (I) as described        previously; especially of general formula (I-A) as described        previously;    -   one second monomer M2 which is n-octyl methacrylate;    -   one third monomer M2 chosen from the group formed by palmityl        methacrylate, stearyl methacrylate, arachidyl methacrylate and        behenyl methacrylate,    -   optionally, one fourth monomer M3 of general formula (X) as        described previously, especially styrene.

Process for Obtaining the Polydiol Copolymers

A person skilled in the art is capable of synthesizing the polydiolrandom copolymers A1 on the basis of his general knowledge.

The copolymerization may be initiated in bulk or in solution in anorganic solvent with free-radical-generating compounds. For example, thecopolymers of the invention are obtained via the known processes ofradical copolymerization, especially controlled radicalcopolymerization, such as the method known as reversibleaddition-fragmentation chain transfer (RAFT) controlled radicalpolymerization and the method known as atom-transfer radicalpolymerization (ATRP). Conventional radical polymerization andtelomerization may also be employed to prepare the polymers of theinvention (Moad, G.; Solomon, D. H., The Chemistry of RadicalPolymerization. 2nd ed.; Elsevier Ltd: 2006; page 639; Matyaszewski, K.;Davis, T. P. Handbook of Radical Polymerization; Wiley-Interscience:Hoboken, 2002; page 936).

According to a preferred embodiment, the copolymerization is performedby conventional radical synthesis, without an RAFT chain-transfer agent.

The polydiol random copolymer A1 is prepared according to a preparationprocess which comprises at least one polymerization step (a) in whichare placed in contact at least:

i) one first monomer M1 of general formula (I) as described previously;ii) at least one second monomer M2 of formula (II) as describedpreviously;iii) at least one third monomer M3 of general formula (X) as describedpreviously;iv) at least one source of free radicals.

In one embodiment, the process may also comprise v) at least onechain-transfer agent.

The term “a source of free radicals” means a chemical compound forgenerating a chemical species bearing one or more unpaired electrons inits outer shell. A person skilled in the art can use any source of freeradicals known per se and suited to polymerization processes, especiallycontrolled radical polymerization processes. Among the sources of freeradicals that are preferred, by way of illustration, are benzoylperoxide, tert-butyl peroxide, diazo compounds such asazobisisobutyronitrile, peroxygenated compounds such as persulfates orhydrogen peroxide, redox systems such as the oxidation of Fe²⁺,persulfate/sodium metabisulfite mixtures, or ascorbic acid/hydrogenperoxide, or alternatively compounds that can be cleaved photochemicallyor by ionizing radiation, for example ultraviolet rays, or by beta orgamma radiation.

The term “chain-transfer agent” means a compound whose purpose is toensure homogeneous growth of macromolecular chains via reversibletransfer reactions between growing species, i.e. polymer chainsterminated with a carbon-based radical, and dormant species, i.e.polymer chains terminated with a transfer agent. This reversibletransfer process makes it possible to control the molecular masses ofcopolymers thus prepared. Preferably, in the process of the invention,the chain-transfer agent comprises a thiocarbonylthio group —S—C(═S)—.As illustrations of chain-transfer agents, mention may be made ofdithioesters, trithiocarbonates, xanthates and dithiocarbamates. Apreferred transfer agent is cumyl dithiobenzoate or 2-cyano-2-propylbenzodithioate.

The term “chain-transfer agent” also means a compound whose purpose isto limit the growth of macromolecular chains undergoing formation byaddition of monomer molecules and to initiate new chains, which makes itpossible to limit the final molecular masses, or even to control them.Such a type of transfer agent is used in telomerization. A preferredtransfer agent is cysteamine.

In one embodiment, the process for preparing a polydiol random copolymercomprises:

-   -   at least one polymerization step (a) as defined above, in which        the monomers M1 and M2 are chosen with X₁ and X₂ representing        hydrogen.

In one embodiment, the polymerization step (a) comprises the placing incontact of at least one monomer M1 with at least two monomers M2 bearingdifferent groups R₃ and at least one monomer M3, preferably styrene.

According to one embodiment (when a radical polymerization has beenperformed with an RAFT chain-transfer agent), after the direct synthesisof the polymer containing the diol functions, the process comprises astep of removing the RAFT chain end by aminolysis followed by Michaeladdition.

The preferences and definitions described for the general formulae (I),(I-A), (I-B), (II-A), (II-B) and (X) also apply to the processesdescribed above.

Properties of the Polydiol Copolymers A1

The polydiol random copolymers A1 are linear copolymers. Alternatively,certain monomers might give access to comb copolymers. The term “combcopolymers” means a copolymer bearing a main chain (also referred to asa backbone) and side chains. The side chains hang on either side of themain chain. The length of each side chain is less than the length of themain chain. FIG. 2 schematically represents a comb polymer.

The copolymers A1 have a backbone of polymerizable functions, especiallya backbone of methacrylate functions and styrene functions, and amixture of hydrocarbon-based side chains optionally substituted withdiol functions.

The monomers of formulae (I), (II) and (X) bear polymerizable functionswhose reactivity leads to the formation of copolymers in which themonomers bearing diol functions are randomly distributed along thebackbone of the copolymer.

The polydiol random copolymers A1 have the advantage of being sensitiveto external stimuli, such as temperature, pressure and shear rate; thissensitivity is reflected by a change in properties. In response to astimulus, the conformation in space of the copolymer chains is modifiedand the diol functions are made more or less accessible to associationreactions, which may generate crosslinking, and also to exchangereactions. These association and exchange processes are reversible. Therandom copolymer A1 is a heat-sensitive copolymer, i.e. It is sensitiveto changes in temperature.

Advantageously, the side chains of the polydiol random copolymer A1 havea mean length ranging from 8 to 20 carbon atoms, preferably from 9 to 18carbon atoms. The term “mean length of the side chain” means the meanlength of the side chains of the monomers M1 of formula (I) and M2 offormula (II) included in the constitution of the copolymer. The sidechains derived from the styrene monomer(s) are not taken into account inthe calculation of the mean lengths of the side chains. A person skilledin the art knows how to obtain this mean length by appropriatelyselecting the types and ratio of monomers constituting the polydiolrandom copolymer. The choice of this mean chain length makes it possibleto obtain a polymer that is soluble in a hydrophobic medium,irrespective of the temperature at which the copolymer is dissolved. Thepolydiol random copolymer A1 is thus miscible in a hydrophobic medium.The term “hydrophobic medium” means a medium that has no affinity orthat has very little affinity for water, i.e. it is immiscible withwater or with an aqueous medium.

Advantageously, the polydiol random copolymer A1 has a molar percentageof monomer M1 of formula (I) in said copolymer ranging from 1% to 30%and preferably from 5% to 25%.

Advantageously, the polydiol random copolymer A1 has a molar percentageof monomer M3 of formula (X), advantageously of styrene, in saidcopolymer ranging from 3% to 40% and more preferably ranging from 5% to35%.

In a preferred embodiment, the polydiol random copolymer A1 has a molarpercentage of monomer M1 of formula (I) in said copolymer ranging from1% to 30%, preferably from 5% to 25%, a molar percentage of monomer(s)M2 of formula (II-B) in said copolymer ranging from 0.1% to 95%,preferably from 5% to 80%, and a molar percentage of monomer M3 offormula (X), advantageously of styrene, in said copolymer ranging from3% to 40%, more preferably ranging from 5% to 35%.

In another preferred embodiment, the polydiol random copolymer A1 has amolar percentage of monomer M1 of formula (I) in said copolymer rangingfrom 1% to 30%, preferably from 5% to 25%, a molar percentage of monomerM2 of formula (II-A) in said copolymer ranging from 8% to 92%, a molarpercentage of monomer M2 of formula (II-B) in said copolymer rangingfrom 0.1% to 62%, and a molar percentage of monomer M3 of formula (X),advantageously of styrene, in said copolymer ranging from 3% to 40%,more preferably ranging from 5% to 35%. The molar percentage of monomersin the copolymer results directly from the adjustment of the amounts ofmonomers used for the synthesis of the copolymer.

Advantageously, the polydiol random copolymer A1 has a number-averagedegree of polymerization ranging from 40 to 2000 and preferably from 40to 1000. In a known manner, the degree of polymerization is controlledusing a controlled radical polymerization technique, a telomerizationtechnique or by adjusting the amount of the source of free radicals whenthe copolymers of the invention are prepared by conventional radicalpolymerization.

Advantageously, the polydiol random copolymer A1 has a polydispersityindex (Ip) ranging from 1.05 to 4.0, preferably ranging from 1.10 to3.8. The polydispersity index is obtained by size exclusionchromatography measurement using poly(methyl methacrylate) calibration.

Advantageously, the polydiol random copolymer A1 has a number-averagemolar mass ranging from 5000 to 400 000 g/mol, preferably from 10 000 to200 000 g/mol, the number-average molar mass being obtained by sizeexclusion chromatography measurement using poly(methyl methacrylate)calibration.

The size exclusion chromatography measurement method using poly(methylmethacrylate) calibration is described in the publication (Fontanille,M.; Gnanou, Y., Chimie et physico-chimie des polymbres [Chemistry andphysical chemistry of polymers] 2nd ed.; Dunod: 2010; page 546).

Compound A2

Boronic Diester Compound A2

In one embodiment, compound A2 comprising two boronic ester functionshas the general formula (III):

in which:

-   -   w₁ and w₂, which may be identical or different, are integers        equal to 0 or 1,    -   R₄, R₅, R₆ and R₇, which may be identical or different, are        chosen from the group formed by hydrogen and a hydrocarbon-based        group comprising from 1 to 30 carbon atoms, preferably between 4        and 18 carbon atoms and even more preferentially between 6 and        14 carbon atoms, said hydrocarbon-based group being optionally        substituted with one or more groups chosen from a hydroxyl and a        group —OJ or —C(O)—O-J with J being a hydrocarbon-based group        comprising from 1 to 24 carbon atoms;    -   L is a divalent bonding group chosen from the group formed by a        C₆-C₁₈ aryl, a C₇-C₂₄ aralkyl and a C₂-C₂₄ hydrocarbon-based        chain, preferably a C₆-C₁₈ aryl.

The term “hydrocarbon-based group comprising from 1 to 30 carbon atoms”means a linear, branched or cyclic alkyl group comprising from 1 to 30carbon atoms, a linear, branched or cyclic alkenyl group comprising from2 to 30 carbon atoms, an aryl group comprising from 6 to 30 carbon atomsor an aralkyl group comprising from 7 to 30 carbon atoms.

The term “hydrocarbon-based group comprising from 1 to 24 carbon atoms”means a linear or branched alkyl group comprising from 1 to 24 carbonatoms or a linear or branched alkenyl group comprising from 2 to 24carbon atoms, an aryl group comprising from 6 to 24 carbon atoms, or anaralkyl group comprising from 7 to 24 carbon atoms. Preferably, Jcomprises from 4 to 18 carbon atoms and preferably between 6 and 12carbon atoms.

The term “C₂-C₂₄ hydrocarbon-based chain” means a linear or branchedalkyl or alkenyl group comprising from 2 to 24 carbon atoms. Preferably,the hydrocarbon-based chain is a linear alkyl group. Preferably, thehydrocarbon-based chain comprises from 6 to 16 carbon atoms.

In one embodiment of the invention, compound A2 is a compound of generalformula (III) above in which:

-   -   w₁ and w₂, which may be identical or different, are integers        equal to 0 or 1;    -   R₄ and R₅ are identical and are hydrogen atoms;    -   R₅ and R₇ are identical and are a hydrocarbon-based group,        preferably a linear alkyl, containing from 1 to 24 carbon atoms,        preferably from 4 to 18 carbon atoms, preferably from 6 to 16        carbon atoms;    -   L is a divalent bonding group and is a C₆-C₁₈ aryl, preferably        phenyl.

The boronic diester compound A2 of formula (III) as described above isobtained via a condensation reaction between a boronic acid of generalformula (III-a) and diol functions of the compounds of general formulae(III-b) and (III-c) according to reaction scheme 4 below:

with w₁, w₂, L, R₄, R₅, R and R₇ as defined above.

Specifically, by condensation of the boronic acid functions of compound(III-a) with diol functions of the compounds of formula (III-b) and offormula (III-c), compounds bearing two boronic ester functions (compoundof formula (III)) are obtained. This step is performed according tomeans that are well known to those skilled in the art.

In the context of the present invention, the compound of general formula(III-a) is dissolved, in the presence of water, in a polar solvent suchas acetone. The presence of water makes it possible to shift thechemical equilibria between the boronic acid molecules of formula(III-a) and the boroxine molecules obtained from the boronic acids offormula (III-a). Specifically, it is well known that boronic acids canspontaneously form boroxine molecules at room temperature. However, thepresence of boroxine molecules is not desirable in the context of thepresent invention.

The condensation reaction is performed in the presence of a dehydratingagent such as magnesium sulfate. This agent traps the water moleculesinitially introduced and also those that are released by thecondensation between the compound of formula (III-a) and the compound offormula (III-b) and between the compound of formula (III-a) and thecompound of formula (III-c).

In one embodiment, compound (III-b) and compound (III-c) are identical.

A person skilled in the art knows how to adapt the amounts of reagentsof formulae (III-b) and/or (III-c) and of formula (III-a) to obtain theproduct of formula (III).

Poly(Boronic Ester) Random Copolymer Compound A2

In another embodiment, compound A2 comprising at least two boronic esterfunctions is a poly(boronic ester) random copolymer resulting from thecopolymerization of at least one monomer M4 of formula (IV) as describedbelow with at least one monomer M5 of formula (V) as described below.

In the rest of the patent application, the expressions “boronic esterrandom copolymer” or “poly(boronic ester) random copolymer” areequivalent and denote the same copolymer.

Monomer M4 of Formula (IV)

The monomer M4 of the boronic ester random copolymer compound A2 has thegeneral formula (IV) in which:

in which:

-   -   t is an integer equal to 0 or 1;    -   u is an integer equal to 0 or 1;    -   M and R₈ are identical or different divalent bonding groups and        are chosen from the group formed by a C₆-C₁₈ aryl, a C₇-C₂₄        aralkyl and a C₂-C₂₄ alkyl, preferably a C₆-C₁₈ aryl,    -   X is a function chosen from the group formed by —O—C(O)—,        —C(O)—O—, —C(O)—N(H)—, —N(H)—C(O)—, —S—, —N(H)—, —N(R′₄)— and        —O— with R′₄ being a hydrocarbon-based chain comprising from 1        to 15 carbon atoms;    -   R₉ is chosen from the group formed by —H, —CH₃ and —CH₂₋CH₃;        preferably —H and —CH₃;    -   R₁₀ and R₁₁, which may be identical or different, are chosen        from the group formed by hydrogen and a hydrocarbon-based group        comprising from 1 to 30 carbon atoms, preferably between 4 and        18 carbon atoms and even more preferentially between 6 and 14        carbon atoms, said hydrocarbon-based group being optionally        substituted with one or more groups chosen from a hydroxyl and a        group —OJ or —C(O)—O-J with J being a hydrocarbon-based group        comprising from 1 to 24 carbon atoms.

The term “C₁-C₂₄ alkyl” means a linear or branched, saturatedhydrocarbon-based chain comprising from 1 to 24 carbon atoms.Preferably, the hydrocarbon-based chain is linear. Preferably, thehydrocarbon-based chain comprises from 6 to 16 carbon atoms.

The term “hydrocarbon-based chain comprising from 1 to 15 carbon atoms”means a linear or branched alkyl or alkenyl group comprising from 1 to15 carbon atoms. Preferably, the hydrocarbon-based chain is a linearalkyl group. Preferably, it comprises from 1 to 8 carbon atoms.

The term “hydrocarbon-based group comprising from 1 to 30 carbon atoms”means a linear, branched or cyclic alkyl group comprising from 1 to 30carbon atoms, a linear, branched or cyclic alkenyl group comprising from2 to 30 carbon atoms, an aryl group comprising from 6 to 30 carbon atomsor an aralkyl group comprising from 7 to 30 carbon atoms.

The term “hydrocarbon-based group comprising from 1 to 24 carbon atoms”means a linear or branched alkyl group comprising from 1 to 24 carbonatoms or a linear or branched alkenyl group comprising from 2 to 24carbon atoms, an aryl group comprising from 6 to 24 carbon atoms, or anaralkyl group comprising from 7 to 24 carbon atoms. Preferably, Jcomprises from 4 to 18 carbon atoms and preferably between 6 and 12carbon atoms.

In one embodiment, the monomer M4 has the general formula (IV) in which:

-   -   t is an integer equal to 0 or 1;    -   u is an integer equal to 0 or 1;    -   M and Re are divalent bonding groups and are different, M is a        C₆-C₁₈ aryl, preferably phenyl, R₈ is a C₇-C₂₄ aralkyl,        preferably benzyl;    -   X is a function chosen from the group formed by —O—C(O)—,        —C(O)—O—, —C(O)—N(H)— and —O—, preferably —C(O)—O— or —O—C(O)—;    -   R₉ is chosen from the group formed by —H and —CH₃, preferably        —H;    -   R₁₀ and R₁₁ are different, one of the groups R₁₀ or R₁₁ is H and        the other group    -   R₁₀ or R₁₁ is a hydrocarbon-based chain, preferably a linear        alkyl group containing from 1 to 24 carbon atoms, preferably        between 4 and 18 carbon atoms, preferably between 6 and 12        carbon atoms.

In one embodiment, the monomer M4 is a styrene monomer. This is the casewhen, in formula (IV): u=1, R₈ is H and Re represents a C₆-C₁₈ aryl or aC₇-C₂₄ aralkyl and the double bond of the monomer M4 of formula (IV) isdirectly connected to the aryl group.

Synthesis of the Monomer M4 of Formula (IV)

In all the schemes presented below, unless otherwise indicated, thevariables R₁₀, R₁₁, M, u, t, X, R₈, R′₄ and R₉ have the same definitionas in formula (IV) above.

The monomers M4 of formula (IV) are especially obtained via apreparation process comprising at least one step of condensation of aboronic acid of general formula (IV-f) with a diol compound of generalformula (IV-g) according to reaction scheme 5 below:

Specifically, by condensation of the boronic acid functions of thecompound of formula (IV-f) with diol functions of the compounds offormula (IV-g) a boronic ester compound of formula (IV) is obtained.This step is performed according to methods that are well known to thoseskilled in the art.

In the context of the present invention, the compound of general formula(IV-f) is dissolved, in the presence of water, in a polar solvent suchas acetone. The condensation reaction is performed in the presence of adehydrating agent such as magnesium sulfate.

The compounds of formula (IV-g) are commercially available from thefollowing suppliers: Sigma-Aldrich®, Alfa Aesar® and TCI®.

The compound of formula (IV-f) is obtained directly from the compound offormula (IV-e) by hydrolysis according to reaction scheme 6 below:

with

-   -   z is an integer equal to 0 or 1;    -   R₁₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;    -   u, X, M, R₈ and R₉ are as defined above.

The compound of formula (IV-e) is obtained by reaction of a compound offormula (IV-c) with a compound of formula (IV-d) according to reactionscheme 7 below:

-   -   z, u, R₁₂, M, R′₄, R₉ and R₈ are as defined above;        and, in this scheme, when    -   X represents —O—C(O)—, then Y₄ represents an alcohol function        —OH or a halogen atom, preferably chlorine or bromine, and Y₅ is        a carboxylic acid function —C(O)—OH;    -   X represents —C(O)—O—, then Y₄ represents a carboxylic acid        function —C(O)—OH and Y₅ is an alcohol function —OH or a halogen        atom, and preferably chlorine or bromine;    -   X represents —C(O)—N(H)—, then Y₄ represents a carboxylic acid        function —C(O)—OH or a function —C(O)-Hal, and Y₅ is an amine        function NH₂;    -   X represents —N(H)—C(O)—, then Y₄ represents an amine function        NH₂ and Y₅ is a carboxylic acid function —C(O)—OH or a function    -   —C(O)-Hal;    -   X represents —S—, then Y₄ is a halogen atom and Y₅ is a thiol        function —SH or Y₄ is a thiol function —SH and Y₅ is a halogen        atom;    -   X represents —N(H)—, then Y₄ is a halogen atom and Y₅ is an        amine function —NH₂ or Y₄ is an amine function —NH₂ and Y₅ is a        halogen atom;    -   X represents —N(R′₄)—, then Y₄ is a halogen atom and Y₅ is an        amine function —N(H)(R′₄) or Y₄ is an amine function —N(H)(R′₄)        and Y₅ is a halogen atom;    -   X represents —O—, then Y₄ is a halogen atom and Y₅ is an alcohol        function —OH or Y₄ is an alcohol function —OH and Y₅ is a        halogen atom.

These esterification, etherification, thioetherification, alkylation orcondensation reactions between an amine function and a carboxylic acidfunction are well known to those skilled in the art. A person skilled inthe art thus knows how to choose, as a function of the chemical natureof the groups Y₁ and Y₂, the reaction conditions to obtain the compoundof formula (IV-e).

The compounds of formula (IV-d) are commercially available from thesuppliers: Sigma-Aldrich®, TCI® and Acros Organics®.

The compound of formula (IV-c) is obtained via a condensation reactionbetween a boronic acid of formula (IV-a) with at least one diol compoundof formula (IV-b) according to reaction scheme 8 below:

with M, Y₄, z and R₁₂ as defined above.

Among the compounds of formula (IV-b), preference is given to the one inwhich R₁₂ is methyl and z=0.

The compounds of formulae (IV-a) and (IV-b) are commercially availablefrom the following suppliers: Sigma-Aldrich), Alfa Aesar® and TCI®.

Monomer M5 of Formula (V):

The monomer M5 of the boronic ester random copolymer compound A2 has thegeneral formula (V)

in which:

-   -   R₁₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   R₁₃ is chosen from the group formed by a C₆-C₁₈ aryl, a C₆-C₁₈        aryl substituted with a group R′₁₃, —C(O)—O—R′₁₃; —O—R′₁₃,        —S—R′₁₃ and —C(O)—N(H)—R′₁₃ with R′₁₃ being a C₁-C₂₅ alkyl        group.

The term “C₁-C₂₅ alkyl group” means a linear or branched, saturatedhydrocarbon-based chain containing from 1 to 25 carbon atoms.Preferably, the hydrocarbon-based chain is linear.

The term “C₆-C₁₈ aryl substituted with a group R₁₃” means an aromatichydrocarbon-based compound comprising from 6 to 18 carbon atoms, atleast one carbon atom of the aromatic ring of which is substituted witha C₁-C₂ alkyl group as defined above.

Among the monomers of formula (V), the monomers corresponding to formula(V-A) are among the preferred:

in which:

-   -   R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃,        preferably —H and —CH₃;    -   R′₁₃ is a C₁-C₂₅ alkyl group, preferably a linear C₁-C₂₅ alkyl,        even more preferably a linear C₅-C₁₅ alkyl.

According to one embodiment, the monomer M5 is a styrene monomer. Thisis the case when, in formula (V): R₁₂ represents H and R₁₃ is chosenfrom the group formed by a C₆-C₁₈ aryl and a C₆-C₁₈ aryl substitutedwith a group R′₁₃ with R′₁₃ being a C₁-C₂₅ alkyl group and the doublebond of the monomer M5 of formula (V) is directly connected to the arylgroup.

Advantageously, according to this embodiment, the monomer M5 is styrene.

Production of the Monomer M5:

The monomers of formulae (V) and (V-A) are well known to those skilledin the art. They are sold by Sigma-Aidrich® and TCI®.

Styrene Monomer:

Advantageously, the copolymer A2 comprises at least one monomer ofstyrene nature, i.e. either styrene, or a styrene derivative, such as astyrene substituted with another group on the aromatic ring.

The monomer M4 may be a styrene monomer when, in formula (IV): u=1, R₉is H and R₈ represents a C₆-C₁₈ aryl or a C₇-C₂₄ aralkyl and the doublebond of the monomer M4 of formula (IV) is directly connected to the arylgroup.

The monomer M5 may also be a styrene monomer when, in formula (V): R₁₂represents H and R₁₃ is chosen from the group formed by a C₆-C₁₈ aryland a C₆-C₁₈ aryl substituted with a group R′₁₃ with R′₁₃ being a C₁-C₂₅alkyl group and the double bond of the monomer M5 of formula (V) isdirectly connected to the aryl group.

When neither M4 nor M5 is of styrene nature, advantageously, thecopolymer A2 comprises at least one third monomer M3 of formula (X)

in which:

-   -   Z₁, Z₂ and Z₃, which may be identical or different, represent        groups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and a group        —OZ′ or —C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl.

M3 has been described in detail above for the preparation of thecopolymer A1.

The preferred monomers M3 and the preferred amounts thereof are the samein A2 as in A1.

Advantageously, when A2 comprises a third monomer M3 of formula (X),this monomer M3 is styrene.

Synthesis of the Poly(Boronic Ester) Random Copolymer Compound A2

A person skilled in the art is capable of synthesizing the boronic esterrandom copolymers on the basis of his or her general knowledge. Thecopolymerization may be initiated in bulk or in solution in an organicsolvent with free-radical-generating compounds. For example, the boronicester random copolymers are obtained via the known processes of radicalcopolymerization, especially controlled radical copolymerization, suchas the method known as reversible addition-fragmentation chain transfer(RAFT) controlled radical polymerization and the method known asatom-transfer radical polymerization (ATRP). Conventional radicalpolymerization and telomerization may also be employed to prepare thepolymers of the invention (Moad, G.; Solomon, D. H., The Chemistry ofRadical Polymerization. 2nd ed.; Elsevier Ltd: 2006; page 639;Matyaszewski, K.; Davis, T. P. Handbook of Radical Polymerization;Wiley-Interscience: Hoboken, 2002; page 936).

The boronic ester random copolymer is prepared according to a processwhich comprises at least one polymerization step (a) in which are placedin contact at least:

i) one first monomer M4 of general formula (IV) as defined previously;ii) at least one second monomer M5 of general formula (V) as definedpreviously;iii) at least one source of free radicals.

In one embodiment, the process may also comprise iv) at least onechain-transfer agent.

The preferences and definitions described for the general formulae (IV)and (V) also apply to the process.

The sources of radicals and the transfer agents are those that have beendescribed for the synthesis of polydiol random copolymers. Thepreferences described the sources of radicals and the transfer agentsalso apply to this process.

Properties of the Poly(Boronic Ester) Random Copolymer Compounds A2

advantageously, the chain formed by the sequence of groups R₁₀, M,(R₈)_(u) with u being an integer equal to 0 or 1, and X of the monomerM4 of general formula (IV) has a total number of carbon atoms rangingfrom 8 to 38 and preferably ranging from 10 to 26.

Advantageously, the side chains of the boronic ester random copolymerhave a mean length of greater than 8 carbon atoms, preferably rangingfrom 11 to 16. This chain length makes it possible to dissolve theboronic ester random copolymer in the hydrophobic medium. The term “meanlength of the side chain” means the mean length of the side chains ofeach monomer constituting the copolymer. The side chains derived fromthe styrene monomer(s) are not taken into account in the calculation ofthe mean lengths of the side chains. A person skilled in the art knowshow to obtain this mean length by appropriately selecting the types andratio of monomers constituting the boronic ester random copolymer.

Advantageously, the boronic ester random copolymer A2 has a molarpercentage of monomer of formula (IV) in said copolymer ranging from0.25% to 30%, preferably from 1% to 25% and better still from 5% to 20%.

Advantageously, the boronic ester random copolymer A2 has a molarpercentage of monomer of formula (IV) in said copolymer ranging from0.25% to 30%, preferably from 1% to 25%, and a molar percentage ofmonomer of formula (V) in said copolymer ranging from 70% to 99.75%,preferably from 75% to 99%.

Advantageously, the boronic ester random copolymer A2 has a molarpercentage of styrene monomer(s), of formulae (IV), (V) and/or (X), insaid copolymer ranging from 2 mol % to 50 mol %, preferentially from 3mol % to 40 mol % and more preferably from 5 mol % to 35 mol %.

The term “molar percentage of styrene monomer(s)” means the sum of thecontents of each of the styrene monomers in the boronic ester randomcopolymer A2, and the styrene monomers may be:

-   -   of formula (IV) when, in formula (IV): u=1, R₉ is H and R₈        represents a C₆-C₁₈ aryl or a C₇-C₂₄ aralkyl and the double bond        of the monomer M4 of formula (IV) is directly connected to the        aryl;    -   of formula (V) when, in formula (V): R₁₂ represents H and R₁₃ is        chosen from the group formed by a C₆-C₁₈ aryl and a C₆-C₁₈ aryl        substituted with a group R′₁₃ with R′₁₃ being a C₁-C₂₅ alkyl        group and the double bond of the monomer M5 of formula (V) is        directly connected to the aryl group,        and/or    -   of formula (X), as explained above.

Advantageously, the boronic ester random copolymer has a number-averagedegree of polymerization ranging from 50 to 1500 and preferably from 50to 800.

Advantageously, the boronic ester random copolymer has a polydispersityindex (Ip) ranging from 1.04 to 3.54, preferably ranging from 1.10 to3.10. These values are obtained by size exclusion chromatography usingtetrahydrofuran as eluent and poly(methyl methacrylate) calibration.

Advantageously, the boronic ester random copolymer has a number-averagemolar mass ranging from 10 000 to 200 000 g/mol, preferably from 25 000to 100 000 g/mol. These values are obtained by size exclusionchromatography using tetrahydrofuran as eluent and poly(methylmethacrylate) calibration.

Compound A2, especially the boronic ester random copolymer, has theproperty of being able to react in a hydrophobic medium, especially anapolar medium, with a compound bearing diol function(s) via atransesterification reaction. This transesterification reaction may berepresented according to scheme 9 below:

Thus, during a transesterification reaction, a boronic ester ofdifferent chemical structure from that of the starting boronic ester isformed by exchange of the hydrocarbon-based groups symbolized by

Exogenous Compound A4

According to one embodiment, the additive composition results from themixing of at least:

-   -   one polydiol random copolymer A1,    -   one random copolymer A2 comprising at least two boronic ester        functions and which can associate with said polydiol random        copolymer A1 via at least one transesterification reaction,    -   one exogenous compound A4 chosen from 1,2-diols and 1,3-diols.

Advantageously, according to this embodiment of the invention, the molarpercentage of exogenous compound A4 in the additive composition,relative to the boronic ester functions of the random copolymer A2ranges from 0.025% to 5000%, preferably from 0.1% to 1000%, even morepreferably from 0.5% to 500% and even more preferably from 1% to 150,%.

The exogenous compound A4 is chosen from 1,2-diols and 1,3-diols. Forthe purposes of the present invention, the term “exogenous compound”means a compound which is added to the additive composition resultingfrom the mixing of at least one polydiol random copolymer A1 and of atleast one compound A2, especially the poly(boronic ester) randomcopolymer,

The exogenous compound A4 may have the general formula (VI):

in which:w3 is an integer equal to 0 or 1,R₁₄ and R₁₅, which may be identical or different, are chosen from thegroup formed by hydrogen and a hydrocarbon-based group containing from 1to 24 carbon atoms, preferably between 4 and 18 carbon atoms, preferablybetween 6 and 12 carbon atoms.

The term “hydrocarbon-based chain comprising from 1 to 24 carbon atoms”means a linear or branched alkyl or alkenyl group comprising from 1 to24 carbon atoms. Preferably, the hydrocarbon-based chain is a linearalkyl group. Preferably, it comprises from 4 to 18 carbon atoms andpreferably between 6 and 12 carbon atoms.

In one embodiment, the exogenous compound A4 has the general formula(VI) in which:

-   -   w₃ is an integer equal to 0 or 1;    -   R₁₄ and R₁₅ are different, one of the groups R₁₄ or R₁₅ is H and        the other group R₁₄ or R₁₅ is a hydrocarbon-based chain,        preferably a linear alkyl group containing from 1 to 24 carbon        atoms, preferably between 4 and 18 carbon atoms, preferably        between 6 and 12 carbon atoms.

In one embodiment, the exogenous compound A4 has a chemical structuredifferent from that of the diol compound A3 released in situ via thetransesterification reaction. In this embodiment, at least one of thesubstituents R₁₄, R₁₅ or the value of the index w₃ of the exogenouscompound A4 of formula (VI) is different, respectively, from thesubstituents R₄ and R₅ or from the value of the index w, or from thesubstituents R₅ and R₇ or from the value of the index w₂ of the boronicdiester compound A2 of formula (III) or is different, respectively, fromthe substituents R₁₀, R₁₁ or from the value of the index t of themonomer (IV) of the poly(boronic ester) random copolymer A2.

In another embodiment, the exogenous compound A4 has a chemicalstructure identical to that of the diol compound A3 released in situ viathe transesterification reaction. In this embodiment, the substituentsR₁₄, R₁₅ and the value of the index w₃ of the exogenous compound A4 offormula (VI) is identical, respectively, to the substituents R₄ and R₅and to the value of the index w, or to R₅ and R₇ and to the value of theindex w₂ of the boronic diester compound A2 of formula (III) or isidentical, respectively, to the substituents R₁₀, R₁₁ and to the valueof the index t of the monomer (IV) of the poly(boronic ester) randomcopolymer A2. According to its temperature of use, the additivecomposition resulting from the mixing of at least one polydiol randomcopolymer A1, of at least one compound A2, especially a random copolymerA2, comprising at least two boronic ester functions and which canassociate with said polydiol random copolymer A1 via atransesterification reaction, and of an addition of at least oneexogenous compound A4 as defined above, may also comprise a diolcompound A3 released in situ, which is identical to the exogenouscompound A4 added to the composition.

For the purposes of the present invention, the term “diol released insitu” means the compound bearing a diol function, this compound beingproduced in the additive composition during the exchange of thehydrocarbon-based groups of the boronic ester compound A2, especially ofthe poly(boronic ester) random copolymer, during the transesterificationreaction. The polydiol random polymer A1 is not a diol released in situwithin the meaning of the present invention.

The compounds of formula (VI) are commercially available from thefollowing suppliers: Sigma-Aldrich®, Alfa Aesar® and TCI®.

Characteristics of the Novel Additive Compositions of the Invention

The additive compositions of the invention resulting from the mixing ofat least one polydiol random copolymer A1 as defined above, of at leastone compound A2 as defined previously, especially of at least onepoly(boronic ester) random copolymer as defined above, and optionally ofat least one exogenous compound A4 as defined above have rheologicalproperties that are very varied as a function of the temperature andaccording to the proportion of the compounds A1, A2 and optionally A4used.

The polydiol random copolymers A1 and the compounds A2 as defined abovehave the advantage of being associative and of exchanging chemical bondsthermoreversibly, especially in a hydrophobic medium, especially in anapolar hydrophobic medium.

Under certain conditions, the polydiol random copolymers A1 and thecompounds A2 as defined above may be crosslinked.

The polydiol random copolymers A1 and the compounds A2 also have theadvantage of being exchangeable.

The term “associative” means that covalent chemical bonds of boronicester type are established between the polydiol random copolymers A1 andthe compounds A2 comprising at least two boronic ester functions,especially with the poly(boronic ester) random copolymer. Depending onthe functionality of the polydiols A1 and of the compounds A2 anddepending on the composition of the mixtures, the formation of covalentbonds between the polydiols A1 and the compounds A2 will optionally beable to lead to the formation of a three-dimensional polymer network.

The term “chemical bond” means a covalent chemical bond of boronic estertype.

The term “exchangeable” means that the compounds are capable ofexchanging chemical bonds between themselves without the total number ornature of the chemical functions being modified. The chemical exchangereaction (transesterification) is illustrated in reaction scheme 10below:

with:

-   -   R being a chemical group of the compound A2,    -   the hatched circle symbolizes the rest of the chemical structure        of compound A2,    -   the cross-ruled rectangle symbolizes the rest of the chemical        structure of the polydiol random copolymer A1.

The boronic ester bonds of the compounds A2, optionally the boronicester bonds formed by transesterification reaction between the boronicesters of the compounds A2 and the exogenous compounds A4, and also theboronic ester bonds formed by association of the polydiol randomcopolymers A1 and of the compounds A2 can exchange with the diolfunctions borne by the compounds A3 released in situ and optionally withdiol functions borne by the exogenous compounds A4 to form novel boronicesters and novel diol functions without the total number of boronicester functions and of diol functions being affected. This otherchemical bond exchange process takes place by metathesis reaction, viasuccessive exchanges of the boronic ester functions in the presence ofdiols. Another chemical bond exchange process is illustrated in FIG. 3,in which it may be observed that the polydiol random copolymer A1-1,which was associated with the polymer A2-1, has exchanged two boronicester bonds with the boronic ester random copolymer A2-2. The polydiolrandom copolymer A1-2, which was associated with the polymer A2-2, hasexchanged two boronic ester bonds with the boronic ester randomcopolymer A2-1; the total number of boronic ester bonds in thecomposition remains unchanged and is equal to 4. The copolymer A1-1 isthen associated with the polymer A2-2. The copolymer A1-2 is thenassociated with the polymer A2-1. The copolymer A2-1 has been exchangedwith the polymer A2-2.

The term “crosslinked” refers to a copolymer in the form of a networkobtained by establishing bridges between the macromolecular chains ofthe copolymer. These chains connected together are for the most partdistributed in the three dimensions of space. A crosslinked copolymerforms a three-dimensional network. In practice, the formation of acopolymer network is confirmed by a solubility test. It may be confirmedthat a copolymer network has been formed by placing the copolymernetwork in a solvent known to dissolve non-crosslinked copolymers of thesame chemical nature. If the copolymer swells instead of beingdissolved, a person skilled in the art knows that a network has beenformed. FIG. 4 illustrates this solubility test.

The term “crosslinkable” refers to a copolymer that is capable of beingcrosslinked.

The term “reversibly crosslinked” refers to a crosslinked copolymerwhose bridges are formed via a reversible chemical reaction. Thereversible chemical reaction can move in one direction or in another,leading to a change of structure of the polymer network. The copolymermay go from an initial non-crosslinked state to a crosslinked state(three-dimensional copolymer network) and from a crosslinked state to anon-crosslinked initial state. In the context of the present invention,the bridges that are formed between the copolymer chains are labile.These bridges may be formed or be exchanged by means of a chemicalreaction that is reversible. In the context of the present invention,the reversible chemical reaction is a transesterification reactionbetween diol functions of a random copolymer (copolymer A1) and boronicester functions of a crosslinking agent (compound A2). The bridgesformed are bonds of boronic ester type. These boronic ester bonds arecovalent and labile due to the reversibility of the transesterificationreaction.

The term “thermoreversibly crosslinked” refers to a copolymer that iscrosslinked by means of a reversible reaction whose movement in onedirection or in the other direction is controlled by the temperature.The mechanism of thermoreversible crosslinking of the composition of theinvention is presented schematically in FIG. 5. At a low temperature,the polydiol copolymer A1 (symbolized by the copolymer bearing functionsA in FIG. 5) is not or is only sparingly crosslinked with the boronicester compounds A2 (symbolized by the compound bearing functions B inFIG. 5). When the temperature increases, the diol functions of copolymerA1 react with the boronic ester functions of compound A2 via atransesterification reaction. The diol random copolymers A1 and thecompounds A2 comprising at least two boronic ester functions then bondtogether and can be exchanged. Depending on the functionality of thepolydiols A1 and of the compounds A2 and depending on the composition ofthe mixtures, a gel may form in the medium, especially when the mediumis apolar. When the temperature decreases again, the boronic ester bondsbetween the polydiol random copolymers A1 and the compounds A2 becomebroken and, as may be the case, the composition loses its gelled nature.

The amount of boronic ester bonds (or boronic ester bond) that can beestablished between the polydiol random copolymers A1 and the compoundsA2 is adjusted by a person skilled in the art by means of an appropriateselection of the polydiol random copolymer A1, of compound A2 and of thecomposition of the mixture.

In addition, a person skilled in the art knows how to select thestructure of compound A2 as a function of the structure of the randomcopolymer A1. Preferably, when, in the random copolymer A1 comprising atleast one monomer M1 in which y=1, then compound A2 of general formula(III) or the copolymer A2 comprising at least one monomer M4 of formula(IV) will preferably be chosen with w, =1, w₂=1 and t=1, respectively.

By controlling the degree of association of the polydiol randomcopolymer A1 and of compound A2, especially of the poly(boronic ester)random copolymer, the viscosity and the rheological behavior of thiscomposition are modified. When it is present, the exogenous compound A4makes it possible to modify the viscosity of this composition as afunction of the temperature and according to the desired use.

In a preferred embodiment of the invention, the exogenous compound A4 isof the same chemical nature as the diol compound A3 released in situ bytransesterification reaction between the polydiol random copolymer A1and compound A2, especially the poly(boronic ester) random copolymer.According to this embodiment, the total amount of free diols present insaid composition is strictly greater than the amount of diol compoundsreleased in situ. The term “free diols” means the diol functions thatare able to form a chemical bond of boronic ester type bytransesterification reaction. For the purposes of the present patentapplication, the term “total amount of free diols” means the totalnumber of diol functions that can form a chemical bond of boronic estertype by transesterification.

According to this embodiment, the total amount of free diols is alwaysequal to the sum of the number of moles of exogenous diol compounds A4and of the number (expressed in mol) of diol functions of the polydiolcopolymer A1. In other words, if, in the additive composition, thereare:

-   -   i mol of exogenous diol compounds A4 and    -   j mol of polydiol random copolymers A1,        the total amount of free diol will be at any instant (thus        irrespective of the degree of association between the polydiol        random copolymer A1 and compound A2, especially the poly(boronic        ester) random copolymer A2)=i+j* the mean number of diols per        random polymer chain A1 (unit: mol).

The amount of diols released in situ in the context of thetransesterification reactions between A1 and A2 is equal to the numberof boronic ester functions connecting the copolymers A1 and A2.

A person skilled in the art knows how to select the chemical structureand the amount of exogenous compounds A4 that he adds to the additivecomposition as a function of the molar percentage of boronic esterfunction of compound A2, especially as a function of the poly(boronicester) random copolymer, to modify the rheological behavior of thecomposition.

Advantageously, the content of random copolymer A1 in the compositionranges from 0.1% to 50.0% by weight relative to the total weight of thecomposition, preferably from 0.25% to 40% by weight relative to thetotal weight of the final composition, and more preferably from 1% to30% by weight relative to the total weight of the final composition.

Advantageously, the content of compound A2 in the composition rangesfrom 0.1% to 50.0% by weight relative to the total weight of thecomposition, preferably from 0.25% to 40% by weight relative to thetotal weight of the final composition, and more preferably from 0.5% to30% by weight relative to the total weight of the final composition.

In one embodiment, the content of random copolymer A1 in the compositionranges from 0.5% to 50.0% by weight relative to the total weight of thecomposition and the content of compound A2, especially of boronic esterrandom copolymer, in the composition ranges from 0.5% to 50.0% by weightrelative to the total weight of the composition.

Preferentially, the mass ratio between the polydiol random compound A1and compound A2 (ratio A1/A2) in the composition ranges from 0.005 to200, preferably from 0.05 to 20 and even more preferably from 0.1 to 10.

In one embodiment, the molar percentage of exogenous compound A4 in theadditive composition ranges from 0.025% to 5000%, preferably from 0.1%to 1000%, more preferably from 0.5% to 500% and even more preferablyfrom 1% to 150% relative to the boronic ester functions of compound A2,especially of the poly(boronic ester) random copolymer. The molarpercentage of exogenous compound A4 relative to the number of boronicester functions of compound A2 is the ratio of the number of moles ofexogenous compound A4 to the number of moles of boronic ester functionof compound A2, the whole multiplied by 100. The number of moles ofboronic ester function of compound A2 may be determined by a personskilled in the art by proton NMR analysis of compound A2, or bymonitoring the conversion into monomers during the synthesis of thecopolymer A2, when compound A2 is a poly(boronic ester) randomcopolymer.

In one preferred embodiment, the composition of the invention is in theform of a stock composition. The term “stock composition” means acomposition from which a person skilled in the art can make daughtersolutions by taking a certain amount of stock solution made up by theaddition of a necessary amount of diluent (solvent or the like) toobtain a desired concentration. A daughter composition is thus obtainedby dilution of a stock composition.

A hydrophobic medium may be a solvent, a mineral oil, a natural oil or asynthetic oil.

In one embodiment, the composition of the invention may also comprise atleast one additive chosen from the group formed by thermoplastics,elastomers, thermoplastic elastomers, thermosetting polymers, pigments,dyes, fillers, plasticizers, fibers, antioxidants, lubricant additives,compatibilizers, antifoams, dispersants additives, adhesion promotersand stabilizers.

Process for Preparing the Novel Additive Compositions of the Invention

The novel additive compositions of the invention are prepared by meansthat are well known to those skilled in the art. For example, itsuffices especially for a person skilled in the art:

-   -   to take a desired amount of a solution comprising the polydiol        random copolymer A1 as defined above;    -   to take a desired amount of a solution comprising compound A2 as        defined above; especially a desired amount of a solution        comprising the poly(boronic ester) random copolymer as defined        previously; and    -   optionally to take a desired amount of a solution comprising the        exogenous compound A4 as defined above;    -   to mix the solutions taken, either simultaneously or        sequentially, to obtain the composition of the invention.

The order of addition of the compounds has no influence in theimplementation of the process for preparing the additive composition.

A person skilled in the art also knows how to adjust the variousparameters of the composition of the invention to obtain either acomposition in which the polydiol random copolymer A1 and compound A2,especially the boronic ester random copolymer, are associated or acomposition in which the polydiol random copolymer A1 and compound A2,especially the boronic ester random copolymer, are crosslinked and tomodify the degree of association or the degree of crosslinking thereoffor a given temperature of use. For example, a person skilled in the artknows especially how to adjust:

-   -   the molar percentage of monomer M1 bearing diol functions in the        polydiol random copolymer A1,    -   the content of styrene monomer M3 in the polydiol random        copolymer A1;    -   the molar percentage of monomer M4 bearing boronic ester        functions in the boronic ester random copolymer A2,    -   the mean length of the side chains of the polydiol random        copolymer A1,    -   the mean length of the side chains of the boronic ester random        copolymer A2,    -   the length of the monomer M4 of the boronic ester random        copolymer A2,    -   the content of styrene monomer M4 of formula (IV) or M5 of        formula (V) or M3 of formula (X) in the boronic ester random        copolymer A2;    -   the length of the boronic diester compound A2;    -   the number-average degree of polymerization of the polydiol        random copolymers A1 and of the boronic ester random copolymers        A2;    -   the mass percentage of the polydiol random copolymer A1;    -   the mass percentage of the boronic diester compound A2;    -   the mass percentage of the boronic ester random copolymer A2,        and, where appropriate:    -   the molar amount of the exogenous compound A4 relative to the        boronic ester functions of compound A2, especially of the        poly(boronic ester) random copolymer,    -   the chemical nature of the exogenous compound A4;    -   the molar percentage of exogenous compound A4;    -   . . . .

Use of the Novel Compositions of the Invention

The compositions of the invention may be used in any medium whoseviscosity varies as a function of the temperature. The compositions ofthe invention make it possible to thicken a fluid and to modify theviscosity as a function of the temperature of use. The additivecomposition according to the invention may be used in fields as variedas assisted oil recovery, the paper industry, paints, food additives,and cosmetic or pharmaceutical formulation.

Lubricant Composition According to the Invention

Another subject of the invention relates to a lubricant compositionresulting from the mixing of at least:

-   -   one lubricant oil,    -   one polydiol random copolymer A1 as defined previously, one        random copolymer A2, as defined previously, comprising at least        two boronic ester functions and which can associate with said        polydiol random copolymer A1 via at least one        transesterification reaction,    -   optionally, one exogenous compound A4 chosen from 1,2-diols and        1,3-diols, and especially as defined previously.

The preferences and definitions described for the general formulae (I),(I-A), (I-B), (II-A), (II-B) and (X) also apply to the polydiol randomcopolymer A1 used in the lubricant compositions of the invention.

The preferences and definitions described for the general formulae (IV)and (V) also apply to the boronic ester random copolymer A2 used in thelubricant compositions of the invention.

The lubricant compositions according to the invention have inversebehavior with respect to modification of the temperature when comparedwith the behavior of the base oil and the rheological additives ofpolymer type of the prior art and have the advantage in that thisrheological behavior may be modified as a function of the temperature ofuse. In contrast with base oil, which becomes fluidized when itstemperature increases, the compositions of the present invention havethe advantage of thickening when the temperature increases. Theformation of the reversible covalent bonds makes it possible to increase(reversibly) the molar mass of the polymers and thus limits the drop inviscosity of the base oil at high temperatures. The additional additionof diol compounds makes it possible to control the degree of formationof these reversible bonds. Advantageously, the viscosity of thelubricant composition is thus controlled and depends less on temperaturefluctuations. In addition, for a given temperature of use, it ispossible to modify the viscosity of the lubricant composition and itsrheological behavior by modifying the amount of diol compounds added tothe lubricant composition. Finally, the lubricant compositions of theinvention have improved thermal stability, improved stability tooxidation, and improved viscosity index, improved resistance to cyclingand better reproducibility of the performance qualities over time.

Lubricant Oil

The term “oil” means a fatty substance that is liquid at roomtemperature (25° C.) and atmospheric pressure (760 mmHg i.e. 10⁵ Pa).

The term “lubricant oil” means an oil which attenuates the frictionbetween two moving parts in order to facilitate the functioning of theseparts. These lubricant oils may be of natural, mineral or syntheticorigin.

The lubricant oils of natural origin may be oils of plant or animalorigin, preferably oils of plant origin such as rapeseed oil, sunfloweroil, palm oil, coconut kernel oil, etc.

The lubricant oils of mineral origin are of petroleum origin and areextracted from petroleum fractions originating from the atmospheric andvacuum distillation of crude oil. The distillation may be followed byrefining operations such as solvent extraction, deasphalting,deparaffinning with solvent, hydrotreatment, hydrocracking,hydroisomerization, hydrofinishing, etc. By way of illustration, mentionmay be made of paraffinic mineral base oils such as the oil Bright StockSolvent (BSS), naphthenic mineral base oils, aromatic mineral oils,hydrorefined mineral bases whose viscosity index is about 100,hydrocracked mineral bases whose viscosity index is between 120 and 130,or hydroisomerized mineral bases whose viscosity index is between 140and 150.

The lubricant oils of synthetic origin (or synthetic bases) originate,as their name indicates, from chemical synthesis, such as the additionof a product to itself or polymerization, or the addition of one productto another product such as esterification, alkylation, fluorination,etc., of components originating from petrochemistry, carbon chemistryand mineral chemistry such as: olefins, aromatics, alcohols, acids,halogen-based, phosphorus-based, silicon-based compounds, etc. By way ofillustration, mention may be made of:

-   -   synthetic oils based on synthetic hydrocarbons such as        poly-alpha-olefins (PAO), internal polyolefins (IPO),        polybutenes and polyisobutenes (PIB), -alkylbenzenes and        alkylated polyphenyls;    -   synthetic oils based on esters such as diacid esters or        neopolyol esters;    -   synthetic oils based on polyglycols, such as monoalkylene        glycols, polyalkylene glycols and polyalkylene glycol mono        ethers;    -   synthetic oils based on phosphate esters;    -   synthetic oils based on silicon derivatives such as silicone        oils or polysiloxanes.

The lubricant oils that may be used in the composition of the inventionmay be chosen from any oil from groups I to V specified in the APIguidelines (Base Oil Interchangeability Guidelines of the AmericanPetroleum Institute (API)) (or equivalents thereof according to theATIEL classification (Association Technique de l'Industrie Europoéennedes Lubrifiants) as summarized below:

Content of Viscosity saturated Sulfur index compounds* content** (VI)***Group I Mineral oils <90% >0.03% 80 ≤ VI > 120 Group II Hydrocrackedoils ≥90% ≤0.03% 80 ≤ VI > 120 Group III ≥90% ≤0.03% ≥120 Hydrocrackedor hydroisomerized oils Group IV (PAO) poly-alpha-olefins Group V Estersand other bases not included in the bases of groups I to IV *measuredaccording to the standard ASTM 02007 **measured according to thestandards ASTM D2622, ASTM D4294, ASTM D4927 and ASTM 03120 ***measuredaccording to the standard ASTM D2270

The compositions of the invention may comprise one or more lubricantoils. The lubricant oil or the lubricant oil mixture is the predominantingredient in the lubricant composition. It is then referred to as thelubricant base oil. The term “predominant ingredient” means that thelubricant oil or the lubricant oil mixture represents at least 51% byweight relative to the total weight of the composition.

Preferably, the lubricant oil or the lubricant oil mixture represents atleast 70% by weight relative to the total weight of the composition.

In one embodiment of the invention, the lubricant oil is chosen from thegroup formed by the oils of group I, of group II, of group III, of groupIV and of group V of the API classification, and a mixture thereof.Preferably, the lubricant oil is chosen from the group formed by theoils of group III, of group IV and of group V of the API classification,and a mixture thereof. Preferably, the lubricant oil is an oil fromgroup III of the API classification.

The lubricant oil as a kinematic viscosity at 100° C. measured accordingto the standard ASTM D445 ranging from 2 to 150 cSt and preferablyranging from 2 to 15 cSt.

Functional Additives

According to one embodiment, the composition of the invention may alsocomprise one or more functional additive chosen from the group formed bydetergents, anti-wear additives, extreme-pressure additives,antioxidants, viscosity-index-enhancing polymers, flow-point improvers,antifoams, thickeners, anticorrosion additives, dispersants, frictionmodifiers, and mixtures thereof.

The functional additive(s) which are added to the composition of theinvention are chosen as a function of the final use of the lubricantcomposition. These additives may be introduced in two different ways:

-   -   either each additive is added individually and sequentially to        the composition,    -   or all of the additives are added simultaneously to the        composition; the additives are, in this case, generally        available in the form of a pack, known as an additive pack.        The functional additive or the mixture of functional additives,        when they are present, represent from 0.1% to 10% by weight        relative to the total weight of the composition.

Detergents:

These additives reduce the formation of deposits on the surface of metalparts by dissolving the oxidation and combustion byproducts. Thedetergents that may be used in the lubricant compositions according tothe present invention are well known to those skilled in the art. Thedetergents commonly used in the formulation of lubricant compositionsare typically anionic compounds including a long lipophilichydrocarbon-based chain and a hydrophilic head. The associated cation istypically a metal cation of an alkali metal or an alkaline-earth metal.The detergents are preferentially chosen from the alkali metal oralkaline-earth metal salts of carboxylic acids, sulfonates, salicylatesand naphthenates, and also phenate salts. The alkali metals andalkaline-earth metals are preferentially calcium, magnesium, sodium orbarium. These metal salts may contain the metal in an approximatelystoichiometric amount or in excess (in an amount greater than thestoichiometric amount). In the latter case, these detergents are knownas overbased detergents. The excess metal giving the overbased nature tothe detergent is in the form of oil-insoluble metal salts, for examplecarbonate, hydroxide, oxalate, acetate or glutamate, preferentiallycarbonate.

Anti-wear additives and extreme-pressure additives:

These additives protect the friction surfaces by forming a protectivefilm adsorbed onto these surfaces. A wide variety of anti-wear andextreme-pressure additives exists. Illustrations that may be mentionedinclude phosphosulfur additives such as metal alkyithiophosphates, inparticular zinc alkylthiophosphates and more specifically zincdialkyldithiophosphates or ZnDTP, amine phosphates, polysulfides,especially sulfur-based olefins and metal dithiocarbamates.

Antioxidants:

These additives retard the degradation of the composition. Degradationof the composition may be reflected by the formation of deposits, thepresence of sludges, or an increase in the viscosity of the composition.Antioxidants act as radical inhibitors or peroxide destroyers. Among theantioxidants commonly employed are antioxidants of phenolic or aminetype.

Anticorrosion Agents:

These additives cover the surface with a film which prevents the accessof oxygen to the surface of the metal. They may occasionally neutralizeacids or certain chemical products to prevent corrosion of the metal. Byway of illustration, examples that may be mentioned includedimercaptothiadlazole (DMTD), benzotriazoles and phosphites (uptake offree sulfur).

Viscosity-Index-Enhancing Polymers:

These additives ensure good cold resistance and a minimum viscosity athigh temperature for the composition. By way of illustration, examplesthat may be mentioned include polymer esters, olefin copolymers (OCP) orpolymethacrylates (PMA).

Flow-Point Improvers:

These additives improve the cold behavior of compositions, by slowingthe formation of paraffin crystals. They are, for example, polyalkylmethacrylates, polyacrylates, polyacrylamides, polyalkylphenols,polyalkylnaphthalenes and polyalkylstyrenes.

Antifoams:

These additives have the effect of countering the effect of thedetergents. Illustrations that may be mentioned includepolymethylsiloxanes and polyacrylates.

Thickeners:

Thickeners are additives used above all for industrial lubrication andmake it possible to formulate lubricants of higher viscosity than enginelubricant compositions. Illustrations that may be mentioned includepolyisobutenes with a weight-average molar mass of from 10 000 to 100000 g/mol.

Dispersants:

These additives ensure the holding in suspension and the removal ofinsoluble solid contaminants constituted by the oxidation byproductsthat are formed during the use of the composition. By way ofillustration, examples that may be mentioned include succinimides, PIB(polyisobutene) succinimides and Mannich bases.

Friction Modifiers:

These additives improve the coefficient of friction of the composition.Illustrations that may be mentioned include molybdenum dithiocarbamate,a means bearing at least one hydrocarbon-based chain of at least 16carbon atoms, and fatty acid esters of polyols such as fatty acid estersof glycerol, in particular glyceryl monooleate.

Process for Preparing the Lubricant Compositions of the Invention

The lubricant compositions of the invention are prepared by means thatare well known to those skilled in the art. For example, it sufficesespecially for a person skilled in the art:

-   -   to take a desired amount of a solution comprising the diol        random copolymer A1 as defined above, especially that resulting        from the copolymerization of at least one monomer of formula (I)        with at least one monomer of formula (II-A) and at least one        monomer of formula (II-B);    -   to take a desired amount of a solution comprising the        poly(boronic ester) random copolymer A2 as defined previously;    -   optionally to take a desired amount of a solution comprising the        exogenous compound A4 as defined above;    -   to mix, either simultaneously or sequentially, the solution is        taken in a lubricant base oil, to obtain the lubricant        composition of the invention.

The order of addition of the compounds has no influence in theimplementation of the process for preparing the lubricant composition.

Properties of the Lubricant Compositions According to the Invention

The lubricant compositions of the invention result from the mixing ofassociative polymers which have the property of increasing the viscosityof the lubricant oil via associations. The lubricant compositionsaccording to the invention have the advantage in that theseassociations, or crosslinking, are thermoreversible and optionally inthat the degree of association or of crosslinking may be controlled bymeans of the addition of an additional diol compound. In addition, theyhave improved thermal stability, and improved viscosity index, improvedstability to oxidation, better cycling performance, and betterreproducibility of the performance qualities over time.

A person skilled in the art knows how to adjust the various parametersof the various constituents of the composition to obtain a lubricantcomposition whose viscosity increases when the temperature increases andto modify the viscosity and the rheological behavior thereof.

The amount of boronic ester bonds (or boronic ester bond) that can beestablished between the polydiol random copolymers A1 and the compoundsA2, especially the boronic ester random copolymer A2, is adjusted by aperson skilled in the art by means of an appropriate selection of thepolydiol random copolymer A1, of compound A2, especially the boronicester random copolymer A2, optionally of the exogenous compound A4, andespecially of the molar percentage of exogenous compound A4.

In addition, a person skilled in the art knows how to select thestructure of compound A2, especially of the boronic ester randomcopolymer, as a function of the structure of the random copolymer A1.Preferably, when, in the random copolymer A1 comprising at least onemonomer M1 in which y=1, then compound A2 of general formula (III) orthe copolymer A2 comprising at least one monomer M4 of formula (IV) willpreferably be chosen with w₁=1, w₂=1 and t=1, respectively.

Moreover, a person skilled in the art knows especially how to adjust:

-   -   the molar percentage of monomer M1 bearing diol functions in the        polydiol random copolymer A1,    -   the molar percentage of monomer M3 of formula (X) in the        polydiol random copolymer A1, especially the molar percentage of        styrene,    -   the molar percentage of monomer M4 bearing boronic ester        functions in the boronic ester random copolymer A2,    -   the mean length of the side chains of the polydiol random        copolymer A1,    -   the mean length of the side chains of the boronic ester random        copolymer A2,    -   the length of the monomer M4 of the boronic ester random        copolymer A2,    -   the mean degree of polymerization of the polydiol random        copolymers A1 and of the boronic ester random copolymers A2,    -   the mass percentage of the polydiol random copolymer A1,    -   the mass percentage of the boronic ester random copolymer A2,    -   optionally, the molar percentage of exogenous compound A4        relative to the boronic ester functions of compound A2,        especially of the poly(boronic ester) random copolymer,    -   . . . .

Advantageously, the content of random copolymer A1 in the lubricantcomposition ranges from 0.25% to 20% by weight relative to the totalweight of the lubricant composition, and preferably from 1% to 10% byweight relative to the total weight of the lubricant composition.

Advantageously, the content of compound A2, especially the content ofboronic ester random copolymer, ranges from 0.25% to 20% by weightrelative to the total weight of the lubricant composition, andpreferably from 0.5% to 10% by weight relative to the total weight ofthe lubricant composition.

Preferentially, the mass ratio (ratio A1/A2) between the polydiol randomcompound A1 and compound A2, especially the boronic ester randomcopolymer, ranges from 0.001 to 100, preferably from 0.05 to 20, evenmore preferably from 0.1 to 10 and more preferably from 0.2 to 5.

In one embodiment, the sum of the masses of the random copolymer A1 andof compound A2 ranges from 0.1% to 50%, advantageously from 0.5% to 20%relative to the total mass of the lubricant composition, preferably from4% to 15% relative to the total mass of the lubricant composition, andthe mass of lubricant oil ranges from 60% to 99% relative to the totalmass of the lubricant composition.

For engine applications, advantageously, the sum of the masses of therandom copolymer A1 and of compound A2 represents from 0.1% to 15%relative to the total mass of the lubricant composition.

For transmission applications, advantageously, the sum of the masses ofthe random copolymer A1 and of compound A2 represents from 0.5% to 50%,relative to the total mass of the lubricant composition.

In one embodiment, the molar percentage of exogenous compound A4 in thelubricant composition ranges from 0.05% to 5000%, preferably from 0.1%to 1000%, more preferably from 0.5% to 500% and even more preferablyfrom 1% to 150% relative to the boronic ester functions of compound A2,especially of the poly(boronic ester) random copolymer.

In one embodiment, the lubricant composition of the invention resultsfrom the mixing of:

-   -   0.5% to 20% by weight of at least one poydiol random copolymer        A1 as defined previously, relative to the total weight of the        lubricant composition;    -   0.5% to 20% by weight of at least one compound A2 as defined        previously, especially of boronic ester random copolymer,        relative to the total weight of the lubricant composition; and    -   optionally 0.001% to 0.5% by weight of at least one exogenous        compound A4 as defined previously, relative to the total weight        of the lubricant composition, and    -   60% to 99% by weight of at least one lubricant oil as defined        previously, relative to the total weight of the lubricant        composition.

In another embodiment, the lubricant composition of the inventionresults from the mixing of:

-   -   0.5% to 20% by weight of at least one polydiol random copolymer        A1 as defined previously, relative to the total weight of the        lubricant composition;    -   0.5% to 20% by weight of at least one compound A2 as defined        previously, especially of boronic ester random copolymer,        relative to the total weight of the lubricant composition; and    -   optionally 0.001% to 0.5% by weight of at least one exogenous        compound A4 as defined previously, relative to the total weight        of the lubricant composition, and    -   0.5% to 15% by weight of at least one functional additive as        defined previously, relative to the total weight of the        lubricant composition, and    -   60% to 99% by weight of at least one lubricant oil as defined        previously, relative to the total weight of the lubricant        composition.

Process for Modifying the Viscosity of a Lubricant Composition

Another subject of the present invention is a process for modifying theviscosity of a lubricant composition, the process comprising at least:

-   -   the provision of a lubricant composition resulting from the        mixing of at least one lubricant oil, of at least one polydiol        random copolymer A1 and of at least one random copolymer A2        comprising at least two boronic ester functions and which can        associate with said polydiol random copolymer A1 via at least        one transesterification reaction.    -   the addition to said lubricant composition of at least one        exogenous compound A4 chosen from 1,2-diols and 1,3-diols.

For the purposes of the present invention, the term “modifying theviscosity of a lubricant composition” means adapting the viscosity at agiven temperature as a function of the use of the lubricant composition.This is obtained by adding an exogenous compound A4 as definedpreviously. This compound makes it possible to control the degree ofassociation and of crosslinking of the two copolymers, polydiol A1 andpoly(boronic ester) A2. Such a process is described in detail in WO2016/113229.

Other Subjects According to the Invention

Another subject of the present invention is the use of the lubricantcomposition as defined above for lubricating a mechanical part.

In the rest of the description, the percentages are expressed on aweight basis relative to the total weight of the lubricant composition.

The compositions of the invention may be used for lubricating thesurfaces of parts that are conventionally found in an engine, such asthe piston system, rings and jackets.

Thus, another subject of the present invention is a composition forlubricating at least one engine, said composition comprising, andespecially consists essentially of, a composition resulting from themixing of:

-   -   85% to 99.9% by weight, advantageously from 92% to 99% by        weight, of a lubricant oil, and    -   0.1% to 15% by weight, advantageously from 1% to 8% by weight,        of a mixture of at least one random copolymer A1 as defined        previously and of at least one boronic ester random copolymer A2        as defined previously; and    -   optionally 0.001% to 0.1% by weight of at least one exogenous        compound A4 as defined previously;        the composition having a kinematic viscosity at 100° C. measured        according to the standard ASTM D445 ranging from 3.8 to 26.1        cSt; the weight percentages being expressed relative to the        total weight of said composition.

In a composition for lubricating at least one engine as defined above,the random copolymers A1, especially the copolymer resulting from thecopolymerization of at least one monomer of formula (I) with at leastone monomer of formula (II-A), at least one monomer of formula (II-B)and at least one monomer M3 of formula (X), and the boronic ester randomcopolymers A2 as defined previously can thermoreversibly associate andexchange, especially in the presence of the exogenous compound A4; butthey do not form three-dimensional networks. They are not crosslinked.

In one embodiment, the composition for lubricating at least one enginealso comprises at least one functional additive chosen from the groupformed by detergents, anti-wear additives, extreme-pressure additives,additional antioxidants, anticorrosion additives,viscosity-index-enhancing polymers, flow-point improvers, antifoams,thickeners, dispersants, friction modifiers, and mixtures thereof.

In one embodiment of the invention, the composition for lubricating atleast one engine, said composition comprising, and especially consistsessentially of, a composition resulting from the mixing of:

-   -   80% to 99% by weight of a lubricant oil, and    -   0.1% to 15% by weight of a mixture of at least one random        copolymer A1 as defined previously and of at least one boronic        ester random copolymer A2 as defined previously; and    -   optionally 0.001% to 0.1% by weight of at least one exogenous        compound A4 as defined previously;    -   0.5% to 15% by weight of at least one functional additive chosen        from the group formed by detergents, anti-wear additives,        extreme-pressure additives, additional antioxidants,        anticorrosion additives, viscosity-index-enhancing polymers,        flow-point improvers, antifoams, thickeners, dispersants,        friction modifiers, and mixtures thereof;        the composition having a kinematic viscosity at 100′C measured        according to the standard ASTM D445 ranging from 3.8 to 26.1        cSt; the weight percentages being expressed relative to the        total weight of said composition.

The definitions and preferences relating to the lubricant oils, to therandom copolymers A1, to the boronic ester random copolymers A2 and tothe exogenous compounds A4 also apply to the compositions forlubricating at least one engine.

Another subject of the present invention is a composition forlubricating at least one transmission, such as manual or automaticgearboxes.

Thus, another subject of the present invention is a composition forlubricating at least one transmission, said composition comprising, andespecially consists essentially of, a composition resulting from themixing of:

-   -   50% to 99.5% by weight of a lubricant oil, and    -   0.5% to 50% by weight of a mixture of at least one random        copolymer A1 as defined previously and of at least one boronic        ester random copolymer A2 as defined previously; and    -   optionally 0.001% to 0.5% by weight of at least one exogenous        compound A4 as defined previously;        the composition having a kinematic viscosity at 100° C. measured        according to the standard ASTM D445 ranging from 4.1 to 41 cSt,        the weight percentages being expressed relative to the total        weight of said composition.

In a composition for lubricating at least one transmission as definedabove, the random copolymers A1 and the boronic ester random copolymersA2 as defined previously can thermoreversibly associate and exchange,especially in the presence of the exogenous compound A4; however, theydo not form three-dimensional networks. They are not crosslinked.

In one embodiment, the composition for lubricating at least onetransmission also comprises at least one functional additive chosen fromthe group formed by detergents, anti-wear additives, extreme-pressureadditives, additional antioxidants, anticorrosion additives,viscosity-index-enhancing polymers, flow-point improvers, antifoams,thickeners, dispersants, friction modifiers, and mixtures thereof.

In one embodiment of the invention, the composition for lubricating atleast one transmission comprises, and especially consists essentiallyof, a composition resulting from the mixing of:

-   -   45% to 99.39% by weight of a lubricant oil, and    -   0.5% to 50% by weight of a mixture of at least one random        copolymer A1 as defined previously and of at least one boronic        ester random copolymer A2 as defined previously; and    -   optionally 0.001% to 0.5% by weight of at least one exogenous        compound A4 as defined previously;    -   0.1% to 15% by weight of at least one functional additive chosen        from the group formed by detergents, anti-wear additives,        extreme-pressure additives, additional antioxidants,        anticorrosion additives, viscosity-index-enhancing polymers,        flow-point improvers, antifoams, thickeners, dispersants,        friction modifiers, and mixtures thereof;        the composition having a kinematic viscosity at 100° C. measured        according to the standard ASTM D445 ranging from 4.1 to 41 cSt,        the weight percentages being expressed relative to the total        weight of said composition.

The definitions and preferences relating to the lubricant oils, to therandom copolymers A1, to the boronic ester random copolymers A2 and tothe exogenous compounds A4 also apply to the compositions forlubricating at least one transmission.

The compositions of the invention may be used for the engines ortransmissions of light vehicles or heavy-goods vehicles, but also ships.

Another subject of the present invention is a process for lubricating atleast one mechanical part, especially at least one engine or at leastone transmission, said process comprising a step in which saidmechanical part is placed in contact with at least one lubricantcomposition as defined above.

The definitions and preferences relating to the lubricant oils, to therandom copolymers A1, to the boronic ester random copolymers A2 and,where appropriate, to the exogenous compounds A4 also apply to theprocess for lubricating at least one mechanical part.

FIGURES

FIG. 1 schematically represents a random copolymer (P1), a gradientcopolymer (P2) and a block copolymer (P3); each circle represents amonomer unit. The difference in chemical structure between the monomersis symbolized by a different color (light gray/black).

FIG. 2 schematically represents a comb copolymer.

FIG. 3 schematically illustrates the exchange reactions of boronic esterbonds between two polydiol random polymers (A1-1 and A1-2) and twoboronic ester random polymers (A2-1 and A2-2) in the presence of diols.

FIG. 4 schematically illustrates and represents the crosslinking of thecomposition according to the invention in tetrahydrofuran (THF).

FIG. 5 schematically represents the behavior of the composition of theinvention as a function of the temperature. A random copolymer (2)bearing diol functions (function A) can thermoreversibly associate witha random copolymer (1) bearing boronic ester functions (function B) viaa transesterification reaction. The organic group of the boronic esterfunctions (function B) which exchanges during the transesterificationreaction is a diol symbolized by a black crescent. It forms a chemicalbond (3) of boronic ester type with release of a diol compound.

FIG. 6 represents the change in relative viscosity (unitless, on they-axis) as a function of the temperature (° C., on the x-axis) ofcompositions A, B, C and D.

FIG. 7 represents the change in relative viscosity (unitless, on they-axis) as a function of the temperature (° C., on the x-axis) ofcompositions A, E and F.

FIG. 8 represents the change in relative viscosity (unitless, on they-axis) as a function of the temperature (° C., on the x-axis) ofcompositions E and F for three successive cycles (−1, −2 and −3) ofheating and then cooling.

FIG. 9 represents the mass (%, on the y-axis) as a function of thetemperature (° C., on the x-axis) of the polydiol A-1a (solid line), ofthe polydiol A-1c (dotted line) and of the polydiol A-1b (dashes) duringa temperature ramp from 25° C. to 600° C. under a dinitrogen atmosphere.

FIG. 10 represents the mass (%, on the y-axis) as a function of time(minutes, on the x-axis) of the polydiol A-1a (solid line), of thepolydiol A-1c (dotted line) and of the polydiol A-1b (dashes) during anisotherm at 150° C. under a dinitrogen atmosphere.

FIG. 11 represents the change in relative viscosity (unitless, on they-axis) as a function of the temperature (° C., on the x-axis) ofcomposition G for three successive cycles (−1, −2 and −3) of heating andthen cooling.

EXPERIMENTAL SECTION

The examples that follow illustrate the invention without limiting it.

1. Synthesis of Random Copolymers A1 Bearing a Diol Function

1.1: Starting with a Monomer Bearing a Diol Function

In one embodiment, the random copolymers A1 of the invention areobtained according to reaction scheme 11 below:

The copolymer obtained after removing the RAFT chain end contains, interalia, styrene as comonomer and the thiocarbonylthio residue was removed,for example by converting it into a thioether.

1.1.1. Synthesis of the Monomer M1 Bearing a Diol Function

The synthesis of a methacrylate monomer bearing a diol function isperformed in three steps (steps 1, 2 and 3 of reaction scheme 11)according to the protocol below:

First Step:

42.1 g (314 mmol) of 1,2,6-hexanetriol (1,2,6-HexTri) are placed in a 1L round-bottomed flask. 5.88 g of molecular sieves (4 Å) are added,followed by 570 mL of acetone. 5.01 g (26.3 mmol) ofpara-toluenesulfonic acid (pTSA) are then slowly added. The reactionmedium is stirred for 24 hours at room temperature. 4.48 g (53.3 mmol)of NaHCO₃ are then added. The reaction medium is stirred for 3 hours atroom temperature before being filtered. The filtrate is thenconcentrated under vacuum using a rotary evaporator until a suspensionof white crystals is obtained. 500 mL of water are then added to thissuspension. The solution thus obtained is extracted with 4×300 mL ofdichloromethane. The organic phases are combined and dried over MgSO₄.The solvent is then totally evaporated off under vacuum at 25° C. usinga rotary evaporator.

Second Step:

5.01 g (28.8 mmol) of the product thus obtained are placed in a 1 Lround-bottomed flask. 4.13 g (31.9 mmol) of DIPEA and 37.9 mg (0.31mmol) of DMAP are then placed in the flask, followed by 5.34 g (34.6mmol) of methacrylic anhydride. The flask is then stirred at roomtemperature for 24 hours. 0.95 g of methanol (29.7 mmol) is then addedto the solution and the flask is stirred for a further 1 hour. Theproduct is then dissolved in 40 mL of hexane. The organic phase is thenwashed successively with 25 mL of water, 3×25 mL of aqueous 0.5 Mhydrochloric acid solution, 3×25 mL of aqueous 0.5 M NaOH solution andagain with 25 mL of water. The organic phase is dried over MgSO₄,filtered and then concentrated under vacuum using a rotary evaporator togive a pale yellow liquid.

Third Step:

17.23 g (71.2 mmol) of the product thus obtained are placed in a 1 Lround-bottomed flask. 90 mL of water and 90 mL of acetonitrile are thenplaced in the flask, followed by 59.1 mL (159 mmol) of acetic acid. Theflask is then stirred for 24 hours at 30° C. while a gentle stream ofnitrogen is bubbled through to force the removal of the acetone. Thesolution thus obtained is extracted with 6×30 mL of ethyl acetate. Theorganic phase is washed successively with 5×30 mL of aqueous 0.5 M NaOHsolution and then 3×30 mL of water. The organic phase is then dried overMgSO₄, filtered and then concentrated under vacuum using a rotaryevaporator to give a pale yellow liquid, the characteristics of whichare as follows:

¹H NMR (400 MHz, CDCl₃) δ: 6.02 (singlet, 1H), 5.49 (singlet, 1H), 4.08(triplet, J=6.4 Hz, 1H), 3.65-3.58 (multiplet, 1H), 3.57-3.50(multiplet, 3H), 3.35 (doublet of doublets, J=7.6 Hz and J=11.2 Hz, 1H),1.86 (doublet of doublets, J=1.2 Hz and J=1.6 Hz, 3H), 1.69-1.31(multiplet. 6H).

1.1.2. Synthesis of Methacrylate Copolymers Bearing Diol Functions withRemoval of the RAFT Chain End

The synthesis of methacrylate copolymers bearing diol functions isperformed in two steps (steps 4 and 5 of reaction scheme 11):

-   -   Copolymerization of two alkyl methacrylate monomers with a        methacrylate monomer bearing a diol function and a styrene        monomer;    -   Removal of the RAFT chain end (aminolysis of the        thiocarbonylthio residue to a thiol followed by Michael addition        of the thiol with an alkyl acrylate).

1.1.2.1 Synthesis of the Copolymer A-1a

More specifically, the synthesis of the copolymer A-1a is performedaccording to the following protocol:

First Step:

12.56 g (37.1 mmol) of stearyl methacrytate (StMA), 12.59 g (49.5 mmol)of lauryl methacrylate (LMA), 2.57 g (24.7 mmol) of styrene (Sty), 2.54g (12.4 mmol) of methacrylate bearing a diol function obtained accordingto the protocol described in section 1.1.1, 82.5 mg (0.30 mmol) of cumyldithiobenzoate, 15 mg (0.09 mmol) of azobisisobutyronitrile (AIBN) and30 mL of anisole are placed in a 250 mL Schlenk tube. The reactionmedium is stirred and degassed for 30 minutes by bubbling nitrogenthrough, and is then maintained at 65° C. for a period of 24 hours.

Second Step:

After 24 hours of polymerization, the Schlenk tube is placed in an icebath to stop the polymerization, and 30 mL of dimethytformamide (DMF)and 0.4 mL of n-butylamine (4 mmol) are added to the solution withoutdegassing the medium. 15 hours later, 3 mL (21 mmol) of butyl acrylateare added. 16 hours later, the polymer isolated by 3 successiveprecipitations in methanol, filtering and drying under vacuum at 50° C.overnight. A copolymer is thus obtained with a number-average molar mass(M_(n)) of 53 000 g/mol, a polydispersity index (Ip) of 1.19 and anumber-average degree of polymerization (DP_(n)) of 253. These valuesare obtained, respectively, by size exclusion chromatography usingtetrahydrofuran as eluent and poly(methyl methacrylate) calibration andby monitoring the monomer conversion during the copolymerization.

A poly(alkyl methacrylate-co-alkyldiol methacrylate-co-styrene)copolymer A-1a containing about 10 mol % of diol monomer units M1(obtained according to the protocol described in section 1.1.1) isobtained.

1.1.2.2 Synthesis of the Copolymer A-1c

The synthesis of the copolymer A-1c is performed according to thefollowing protocol:

12.51 g (36.9 mmol) of stearyl methacrylate (StMA), 12.65 g (49.7 mmol)of lauryl methacrylate (LMA), 2.58 g (24.7 mmol) of styrene, 2.51 g(12.4 mmol) of methacrylate bearing a diol function obtained accordingto the protocol described in section 1.1.1, 15.3 mg (0.06 mmol) of cumyldithiobenzoate, 4.6 mg (0.03 mmol) of AIBN and 3.2 mL of anisole areplaced in a 100 mL Schlenk tube. The reaction medium is stirred anddegassed for 30 minutes by bubbling nitrogen through, and is thenmaintained at 65° C. for a period of 24 hours.

After 24 hours of polymerization, the Schlenk tube is placed in an icebath to stop the polymerization, and 20 mL of DMF, 30 mL oftetrahydrofuran (THF) and 0.27 mL of n-butylamine (2.7 mmol) are addedto the solution. 16 hours later, 4 mL (28 mmol) of butyl acrylate areadded. 24 hours later, the polymer is isolated by 3 successiveprecipitations in methanol and drying under vacuum at 50° C. overnight.A copolymer is thus obtained with a number-average molar mass (M_(n)) of154 000 g/mol, a polydispersity index (Ip) of 1.23 and a number-averagedegree of polymerization (DP_(n)) of 893. These values are obtained,respectively, by size exclusion chromatography using THF as eluent andpoly(methyl methacrylate) calibration and by monitoring the monomerconversion during the copolymerization.

A poly(alkyl methacrylate-co-alkyldiol methacrylate-co-styrene)copolymer A-1c containing about 9 mol % of diol monomer units isobtained.

1.1.3. Synthesis of Methacrylate Copolymers Bearing Diol Functionswithout RAFT Chain Removal

The synthesis of the methacrylate copolymers bearing diol functions andnot having improved properties when compared with the copolymers of theprior art is performed in a single step which consists of thecopolymerization of two alkyl methacrylate monomers with a methacrylatemonomer bearing a diol function. The term “methacrylate copolymers nothaving improved properties when compared with the copolymers of theprior art” means methacrylate copolymers bearing diol functions notcontaining any styrene monomer and always bearing the thiocarbonylthioresidue at the chain end. This copolymer is representative ofmethacrylate copolymers bearing diol functions obtained by following theprotocol described in patent application WO 2015/110642 (experimentalsection § 1.).

More specifically, the synthesis of the copolymer A-1b is performedaccording to the following protocol:

First Step:

13.38 g (39.5 mmol) of stearyl methacrylate (StMA), 12.58 g (49.4 mmol)of lauryl methacrylate (LMA), 2.01 g (9.9 mmol) of methacrylate bearinga diol function obtained according to the protocol described in section1.1.1, 93.7 mg (0.34 mmol) of cumyl dithiobenzoate, 12.4 mg (0.08 mmol)of azobisisobutyronitrile (AIBN) and 28 mL of anisole are placed in a250 mL Schlenk tube. The reaction medium is stirred and degassed for 30minutes by bubbling nitrogen through, and is then maintained at 65° C.for a period of 18 hours 30 minutes. The polymer is then isolated by 3successive precipitations in methanol, filtering and drying under vacuumat 50° C. overnight. A copolymer is thus obtained with a number-averagemolar mass (M_(n)) of 56 700 g/mol, a polydispersity index (Ip) of 1.21and a number-average degree of polymerization (DP) of 253. These valuesare obtained, respectively, by size exclusion chromatography usingtetrahydrofuran as eluent and poly(methyl methacrylate) calibration andby monitoring the monomer conversion during the copolymerization. Apoly(alkyl methacrylate-co-alkyldiol methacrylate) copolymer A-1bcontaining about 10 mol % of diol monomer units M1 is obtained.

2. Synthesis of the Poly(Alkyl Methacrylate-Co-Boronic Ester Monomer)Copolymer

This synthesis is performed according to the protocol described inpatent application WO 2016/113229 (experimental section § 2.).

3. Rheological Studies

3.1 Ingredients for the Formulation of Compositions A to F LubricantBase Oil

The lubricant base oil used in the test compositions is an oil fromgroup III of the API classification, sold by SK under the name Yubase 4.It has the following characteristics:

-   -   Its kinematic viscosity at 40° C. measured according to the        standard ASTM D445 is 19.57 cSt;    -   Its kinematic viscosity measured at 100° C. according to the        standard ASTM D445 is 4.23 cSt;    -   Its viscosity index measured according to the standard ASTM        D2270 is 122;    -   Its Noack volatility, as a weight percentage, measured according        to the standard DIN 51581 is 15;    -   Its flash point in degrees Celsius measured according to the        standard ASTM D92 is 230° C.;    -   Its pour point in degrees Celsius measured according to the        standard ASTM D97 is −15° C.    -   Polydiol Random Copolymer A-1a (According to 61.1.2)

This copolymer comprises 10 mol % of monomer bearing a diol function and24 mol % of styrene monomer. The mean side chain length is 13.5 carbonatoms. Its number-average molar mass is 53 000 g/mol. Its polydispersityindex is 1.19. Its number-average degree of polymerization (DP_(n)) is253. The number-average molar mass and the polydispersity index aremeasured by size exclusion chromatography measurement using poly(methylmethacrylate) calibration. This copolymer is obtained by performing theprotocol described in section 1.1.2.1 above.

Polydiol Random Copolymer A-1c (According to 61.1.2)

This copolymer comprises 9 mol % of monomer bearing a diol function and26 mol % of styrene monomer. The mean side chain length is 13.5 carbonatoms. Its number-average molar mass is 154 000 g/mol. Itspolydispersity index is 1.23. Its number-average degree ofpolymerization (DP_(n)) is 893. The number-average molar mass and thepolydispersity index are measured by size exclusion chromatographymeasurement using poly(methyl methacrylate) calibration. This copolymeris obtained by performing the protocol described in section 1.1.2.2above.

Boronic Ester Random Copolymer A-2:

This copolymer comprises 5 mol % of monomers bearing boronic esterfunctions. The mean side chain length is 12 carbon atoms. Itsnumber-average molar mass is 39 000 g/mol. Its polydispersity index is1.41. Its number-average degree of polymerization (DP_(n)) is 192. Itsnumber-average molar mass and the polydispersity index are measured bysize exclusion chromatography measurement using poly(methylmethacrylate) calibration. This copolymer is obtained by performing theprotocol described in section 2 above.

-   -   Polydiol Random Copolymer A-1b (According to 1.1.2)

This copolymer comprises 10 mol % of monomer bearing a diol (and doesnot contain any styrene). The mean side chain length is 13.8 carbonatoms. Its number-average molar mass is 56 700 g/mol. Its polydispersityindex is 1.21. Its number-average degree of polymerization (DP_(n)) is253. The number-average molar mass and the polydispersity index aremeasured by size exclusion chromatography measurement using poly(methylmethacrylate) calibration. This copolymer is obtained by performing theprotocol described in section 1.1.3 above.

3.2 Formulation of Compositions for the Viscosity Study Composition A(Comparative) is Obtained in the Following Manner:

It contains a solution containing 4.20% by mass of a polymethacrylatepolymer in a lubricant base oil from group III of the APIclassification. The polymer has a number-average molar mass (M_(n))equal to 106 000 g/mol, a polydispersity index (Ip) equal to 3.06, anumber-average degree of polymerization of 466 and the mean side chainlength is 14 carbon atoms.

This polymethacrylate is used as viscosity-index-enhancing additive.4.95 g of a formulation with a mass concentration of 42% of thispolymethacrylate in a group III base oil and 44.6 g of group III baseoil are placed in a flask. The solution thus obtained is stirred at 90°C. until the polymethacrylate has fully dissolved.

A solution containing 4.20% by mass of this polymethacrylate isobtained. This composition is used as reference for the viscosity study.It represents the rheological behavior of commercial lubricantcompositions.

Composition B (Comparative) is Obtained in the Following Manner:

6.52 g of polydiol copolymer A-1a (according to § 1.1.1) and 58.68 g ofa group III base oil are placed in a flask. The solution thus obtainedis stirred at room temperature until the polydiol A-1a has fullydissolved. A solution containing 10% by mass of polydiol copolymer A-1ais obtained.

4.20 g of this solution of polydiol A-1a at 10% by mass in the group IIIbase oil are mixed with 2.80 g of this same base oil. The solution thusobtained is stirred at room temperature for 5 minutes. A solutioncontaining 6% by mass of polydiol copolymer A-1a is obtained.

Composition C (Comparative) is Obtained in the Following Manner:

7.33 g of poly(boronic ester) copolymer A-2 and 65.97 g of a group IIIbase oil are placed in a flask. The solution thus obtained is stirred atroom temperature until the poly(boronic ester) A-2 has fully dissolved.A solution containing 10% by mass of poly(boronic ester) copolymer A-2is obtained.

4.20 g of this solution of poly(boronic ester) A-2 at 10% by mass in thegroup III base oil are mixed with 2.80 g of this same base oil. Thesolution thus obtained is stirred at room temperature for 5 minutes. Asolution containing 6% by mass of poly(boronic ester) copolymer A-2 isobtained.

Composition D (Comparative) is Obtained in the Following Manner.

4.10 g of polydiol copolymer A-1b (according to § 1.1.2) and 36.90 g ofa group III base oil are placed in a flask. The solution thus obtainedis stirred at room temperature until the polydiol A-1b has fullydissolved. A solution containing 10% by mass of polydiol copolymer A-1bis obtained.

4.20 g of this solution of polydiol A-1b at 10% by mass in the group IIIbase oil are mixed with 2.80 g of this same base oil. The solution thusobtained is stirred at room temperature for 5 minutes. A solutioncontaining 6% by mass of polydiol copolymer A-1b is obtained.

Composition E (According to the Invention) is Obtained in the FollowingManner:

2.80 g of the solution containing 10% by mass of polydiol A-1a preparedpreviously and 1.4 g of group III base oil are placed in a flask. 2.80 gof the solution containing 10% by mass of poly(boronic ester) A-2prepared previously are added to this solution. The solution thusobtained is stirred at room temperature for 5 minutes. A solutioncontaining 4% by mass of polydiol copolymer A-1a and 4% by mass ofpoly(boronic ester) copolymer A-2 is obtained.

Composition F (Comparative) is Obtained in the Following Manner

2.80 g of the solution containing 10% by mass of polydiol A-1b preparedpreviously and 1.40 g of group III base oil are placed in a flask. 2.80g of the solution containing 10% by mass of poly(boronic ester) A-2prepared previously are added to this solution. The solution thusobtained is stirred at room temperature for 5 minutes. A solutioncontaining 4% by mass of polydiol copolymer A-1b and 4% by mass ofpoly(boronic ester) copolymer A-2 is obtained.

Composition G (According to the Invention) is Obtained in the FollowingManner.

1.05 g of the solution containing 10% by mass of polydiol A-1c preparedpreviously and 5.25 g of group III base oil are placed in a flask. 0.70g of the solution containing 10% by mass of poly(boronic ester) A-2prepared previously are added to this solution. The solution thusobtained is stirred at room temperature for 5 minutes. A solutioncontaining 1.5% by mass of polydiol copolymer A-1c and 1% by mass ofpoly(boronic ester) copolymer A-2 is obtained.

3.3 Apparatus and Protocol for Measuring the Viscosity

The rheological studies were performed using a Couette MCR 501controlled stress rheometer from the company Anton Paar.

In the case of the polymer formulations which do not form gels in agroup III base oil over the temperature range of the study (compositionsA to F), the rheology measurements were performed using a cylindricalgeometry of reference DG 26.7. The viscosity was measured as a functionof the shear rate for a temperature range extending from 10° C. to150′C. For each temperature, the viscosity of the system was measured asa function of the shear rate from 1 to 100 s⁻¹. The measurements of theviscosity as a function of the shear rate at T=10° C., 50° C., 70° C.,110° C., 130° C. and 150° C. were performed (going from 10° C. to 150°C.). A mean viscosity was then calculated for each temperature using themeasurement points located on the same plateau.

The relative viscosity calculated according to the following formula

$\left( {\eta_{relative} = \frac{\eta_{solution}}{\eta_{{base}\mspace{14mu} {oil}}}} \right)$

was chosen to represent the change in viscosity of the system as afunction of the temperature, since this magnitude directly reflects thecompensation for the natural viscosity loss of a group III base oil ofthe polymer systems studied.

3.4 Rheological Results Obtained

The relative viscosity of compositions A, E and F was studied for atemperature range extending from 10° to 150° C. whereas that ofcompositions B, C and D was studied between 10° C. and 110° C. In thecases where the viscosity was not perfectly constant with the shearrate, the viscosity of the solution was calculated by taking the mean ofthe viscosities obtained on all the shear rates. The relative viscosityof these compositions is illustrated in FIGS. 6, 7 and 8. Copolymer A-1aalone in composition B does not allow a significant compensation for thenatural viscosity loss of the group III base oil (FIG. 6). This islikewise the case for the poly(boronic ester) copolymer A-2 when it isused alone in composition C or else for the polydiol copolymer A-1b whenit is used alone in composition D (FIG. 6).

When the polydiol random copolymer A-1a and the poly(boronic ester)copolymer A-2 are present together in the same lubricant composition(composition E), compensation for the natural viscosity loss of thegroup III base oil which is greater than that which results from theaddition of the polymer methacrylate polymer to the group III base oil(composition A) at 150° C. is observed (FIG. 7). At the same time,composition E shows a lower relative viscosity than composition A(reference polymethacrylate) at 10° C. (FIG. 7). The relative viscosityvalues are also represented for three successive cycles ofheating-cooling between 10′C to 150° C. (E-1, E-2 and E-3). These valueschange slightly in the course of the 3 cycles, but still give anincrease in the relative viscosity of about 1 between 10° C. and 150°C., reflecting the great compensation for the natural viscosity loss ofthe group III base oil over this temperature range (FIG. 8).

When the polydiol random copolymer A-1b and the poly(boronic ester)copolymer A-2 are present together in the same lubricant composition(composition F), a slight compensation for the natural viscosity loss ofthe group III base oil is observed (FIG. 7). This compensation is lowerthan in the case of composition E. The relative viscosity values arealso represented for the first three successive cycles from 10° C. to150° C. (F-1, F-2 and F-3). During the first cycle, composition F givesrelative viscosity values that are virtually identical to those ofcomposition E from 10° C. to 110° C. On the other hand, when thetemperature reaches 130° C. and then 150° C. during the first heatingcycle, the relative viscosity drops substantially (FIG. 8). The next twocycles (F-2, F-3) give comparable relative viscosities and an increasein the relative viscosity when the temperature increases (FIG. 8). Forthese two cycles an increase in relative viscosity of less than 0.5 isreached between 10° C. and 150° C. This result shows that composition Fappears to be degraded after its first passage beyond 110° C. The effectof this degradation is to reduce the compensation for the naturalviscosity loss of the oil obtained with this composition (up to 110° C.in the first cycle). The change in composition of the polydiol (additionof styrene and removal of the RAFT chain end) thus made it possible tomaintain the rheological properties of composition E for several cyclesabove 110° C.

The relative viscosity values for formulation G are represented forthree successive cycles of heating-cooling between 10° C. to 150° C.(G-1, G-2 and G-3) in FIG. 11. These values change slightly in thecourse of the three cycles, but still give an increase in the relativeviscosity of about 0.55 between 10° C. and 150° C., reflecting the greatcompensation for the natural viscosity loss of the group III base oilover this temperature range. Furthermore, irrespective of the cycle, thecomposition gives a relative viscosity ranging from about 1.3 at 10° C.to about 1.85 at 150° C. Composition G thus appears to be more stablethan composition F for this study.

4. Thermogravimetric Studies

4.1 Apparatus and Protocols for Thermogravimetric Analysis (TGA)

The thermogravimetric studies were performed using a TG 209 F1thermogravimetric analyzer from the company Netzsch. The experimentswere performed under a stream of 20 mL/minute of dinitrogen. 15 to 30 mgof polymers are placed in an aluminum crucible before each analysis.

The isotherms were applied for 20 hours at 150° C., whereas the rampswere applied from 25° C. to 600° C. at a heating rate of 10° C./minute.

4.2 TGA Results

The thermal stability of the polydiol A-1a, of the polydiol A-1c and ofthe polydiol A-1b was studied under a dinitrogen atmosphere via twodifferent protocols. Firstly, the polydiols were subjected to atemperature ramp from 25° C. to 600° C. so as to observe the change inmass of the samples as a function of the temperature (FIG. 9). Secondly,the polydiols were subjected to an isotherm at 150° C. for 20 hours soas to the change in mass as a function of time under these conditions(FIG. 10).

During the temperature ramp from 25° C. to 600° C., the polydiol A-1aloses 1% of its mass at 290° C. and 5% of its mass at 335° C. and thepolydiol A-1c loses 1% of its mass at 240° C. and 5% of its mass at 310°C., whereas the polydiol A-1b loses 1% of its mass at 220° C. and 5% ofits mass at 290° C. (FIG. 9). Above 320° C., the three polydiols show avery rapid loss of mass leading to total degradation of these polymersat 450° C. Initiation of the loss of mass thus takes place at lowertemperatures for the polydiol A-1b than for the polydiol A-1a and thepolydiol A-1c.

Even during the isotherm of 20 hours at 150° C., the polydiol A-1a loses0.8% of its mass after 2 hours and 1.1% of its mass after 20 hours andthe polydiol A-1c loses 0.4% of its mass after 2 hours and 0.4% of itsmass after 20 hours, whereas the polydiol A-1b loses 1% of its massafter 2 hours and 3.3% of its mass after 20 hours (FIG. 10). It isprobable that the loss of mass which takes place at the start of theisotherm is attributable to the loss of water which has been adsorbedonto the polymers. This result shows that the polydiol A-1b has agreater loss of mass than the polydiol A-1a and the polydiol A-1c duringthis isotherm. Furthermore, a constant rate of loss of mass appears tobecome established after 4 hours of isotherm for the polydiol A-1a andafter 7 hours of isotherm for the polydiol A-1b. The polydiol A-1a has aloss of mass of 0.009%/hour, whereas the polydiol A-1b reaches a rate of0.037%/hour (FIG. 10). The polydiol A-1c does not show any significantloss of mass after 3 hours of isotherm at 150° C. This measurementindicates that the polydiol A-1 b degrades more rapidly than thepolydiol A-1a and the polydiol A-1c under these conditions.

1-22. (canceled)
 23. A composition resulting from the mixing of at leastone polydiol random copolymer A1 comprising at least from 2 mol % to 50mol % of at least one monomer M3 of general formula (X):

(X) in which: Z₁, Z₂ and Z₃, which may be identical or different,represent groups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and agroup —OZ′ or —C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl. and a compound A2comprising at least two boronic ester functions.
 24. The composition asclaimed in claim 23, in which the polydiol random copolymer A1 is acopolymer resulting from the copolymerization: of at least one firstmonomer M1 of general formula (I):

in which: R₁ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃; xis an integer ranging from 1 to 18; y is an integer equal to 0 or 1; X₁and X₂, which may be identical or different, are chosen from the groupformed by hydrogen, tetrahydropyranyl, methyloxymethyl, tert-butyl,benzyl, trimethylsilyl and t-butyldimethylsilyl; or X₁ and X₂ form, withthe oxygen atoms, a bridge having the following formula

in which: the asterisks (*) symbolize the bonds to oxygen atoms, R′₂ andR″₂, which may be identical or different, are chosen from the groupformed by hydrogen and a C₁-C₁₁ alkyl; or X₁ and X₂ form, with theoxygen atoms, a boronic ester having the following formula:

in which: the asterisks (*) symbolize the bonds to oxygen atoms, R′″₂ ischosen from the group formed by a C₆-C₃₀ aryl, a C₇-C₃₀ aralkyl and aC₂-C₃₀ alkyl; with at least one second monomer M2 of general formula(II):

in which: R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;R₃ is chosen from the group formed by: —C(O)—O—R′₃; O—R′₃; —S—R′₃ and—C(O)—N(H)—R′₃ with R′₃ being a C₁-C₃₀ alkyl group, and with at leastone third monomer M3 of general formula (X):

in which: Z₁, Z₂ and Z₃, which may be identical or different, representgroups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and a group —OZ′ or—C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl.
 25. The composition as claimedin claim 23, in which the third monomer M3 is styrene.
 26. Thecomposition as claimed in claim 24, in which the random copolymer A1results from the copolymerization of at least one monomer M1 with atleast two monomers M2 bearing different groups R₃ and at least onemonomer M3.
 27. The composition as claimed in claim 26, in which the twomonomers M2 of the random copolymer A1 have the general formula (II-B):

in which: R₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;R′″₃ is a C₉-C₃₀ alkyl group.
 28. The composition as claimed in claim24, in which the side chains of the random copolymer A1 have a meanlength ranging from 8 to 20 carbon atoms.
 29. The composition as claimedin claim 24, in which the random copolymer A1 has a molar percentage ofmonomer M1 of formula (I) in said copolymer ranging from 1% to 30%. 30.The composition as claimed in claim 23, in which the random copolymer A1has a number-average degree of polymerization ranging from 40 to 2000and a polydispersity index (Ip) ranging from 1.05 to 4.0.
 31. Thecomposition as claimed in claim 23, in which compound A2 is a compoundof formula (III):

in which: w₁ and w₂, which may be identical or different, are integerschosen between 0 and 1; R₄, R₅, R₆ and R₇, which may be identical ordifferent, represent a group chosen from a hydrogen atom, ahydrocarbon-based group comprising from 1 to 30 carbon atoms, optionallysubstituted with one or more groups chosen from: a hydroxyl, a group —OJor —C(O)—O-J with J being a hydrocarbon-based group comprising from 1 to24 carbon atoms; L is a divalent bonding group chosen from the groupformed by a C₆-C₁₈ aryl, a C₆-C₈ aralkyl and a C₂-C₂₄ hydrocarbon-basedchain.
 32. The composition as claimed in claim 23, in which compound A2is a random copolymer resulting from the copolymerization of at leastone monomer M4 of formula (IV):

in which: t is an integer equal to 0 or 1; u is an integer equal to 0 or1; M and R₈ are identical or different divalent bonding groups, chosenfrom the group formed by C₆-C₁₈ aryl, a C₇-C₂₄ aralkyl and a C₂-C₂₄alkyl, X is a function chosen from the group formed by —O—C(O)—,—C(O)—O—, —C(O)—N(H)—, —N(H)—C(O)—, —S—, —N(H)—, —N(R′₄)— and —O— withR′₄ being a hydrocarbon-based chain comprising from 1 to 15 carbonatoms; R₉ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃; R₁₀and R₁₁, which may be identical or different, represent a group chosenfrom a hydrogen atom, a hydrocarbon-based group comprising from 1 to 30carbon atoms, optionally substituted with one or more groups chosenfrom: a hydroxyl, a group —OJ or —C(O)—O-J with J being ahydrocarbon-based group comprising from 1 to 24 carbon atoms; with atleast one second monomer M5 of general formula (V):

in which: R₁₂ is chosen from the group formed by —H, —CH₃ and —CH₂—CH₃;R₁₃ is chosen from the group formed by a C₆-C₁₈ aryl, a C₆-C₁₈ arylsubstituted with a group R′₁₃, —C(O)—O—R′₁₃; —O—R′₁₃, —S—R′₁₃ and—C(O)—N(H)—R′₁₃ with R′₁₃ being a C₁-C₃₀ alkyl group.
 33. Thecomposition as claimed in claim 32, in which at least one of thefollowing three conditions is met: either, in formula (IV): u=1, R₉ is Hand R₈ represents a C₆-C₁₈ aryl or a C₇-C₂₄ aralkyl and the double bondof the monomer M4 of formula (IV) is directly connected to the arylgroup; or, in formula (V): R₁₂ represents H and R₁₃ is chosen from thegroup formed by a C₆-C₁₈ aryl and a C₆-C₁₈ aryl substituted with a groupR′₁₃ with R′₁₃ being a C₁-C₂₅ alkyl group and the double bond of themonomer M5 of formula (V) is directly connected to the aryl group. or,copolymer A2 comprises at least one third monomer M3 of formula (X)

in which: Z₁, Z₂ and Z₃, which may be identical or different, representgroups chosen from a hydrogen atom, a C₁-C₁₂ alkyl, and a group —OZ′ or—C(O)—O—Z′ with Z′ being a C₁-C₁₂ alkyl.
 34. The composition as claimedin claim 32, in which the chain formed by the sequence of groups R₁₀, M,X and (R₈)_(u) with u equal to 0, in which the chain formed by thesequence of groups R₁₀, M, X and (R₈)_(u) with u equal to 0 or 1 of themonomer of formula (IV) has a total number of carbon atoms ranging from8 to
 38. 35. The composition as claimed in claim 32, in which the sidechains of copolymer A2 have a mean length of greater than or equal to 8carbon atoms.
 36. The composition as claimed in claim 32, in whichcopolymer A2 has a molar percentage of monomer of formula (IV) in saidcopolymer ranging from 0.25% to 30%.
 37. The composition as claimed inclaim 32, in which copolymer A2 has a number-average degree ofpolymerization ranging from 50 to 1500 and a polydispersity index (Ip)ranging from 1.04 to 3.54.
 38. The composition as claimed in claim 23,in which the content of copolymer A1 ranges from 0.1% to 50% by weightrelative to the total weight of the composition.
 39. The composition asclaimed in claim 23, in which the content of compound A2 ranges from0.1% to 50% by weight relative to total weight of the composition. 40.The composition as claimed in claim 23, in which the mass ratio betweencopolymer A1 and compound A2 (ratio A1/A2) ranges from 0.005 to
 200. 41.The composition as claimed in claim 23, which also comprises at leastone exogenous compound A4 chosen from 1,2-diols and 1,3-diols.
 42. Alubricant composition resulting from the mixing of at least: onelubricant oil; and one composition as defined in claim 23.